Noriko Okazaki helps keep Japan Inc. in business

You wouldn't exactly mention Noriko Okazaki in the same breath with Sony or Mitsubishi. But in her way, the energetic housewife and mother of two plays just as important a role in keeping the Japanese economy strong as the giant corporations do.

Mrs. Okazaki is a ''part time'' worker - one of millions of women who provide Japanese industry with a unique method of fine tuning to cope with the constant rises and falls of economic activity.

The real value of her contribution, however, isn't so much in the work she performs as in the mere fact that she is willing to work at all.

Part time in Japan doesn't have quite the same connotation as in the United States. Here, it does not necessarily include those who only work for part of the day or week. Instead, it refers to persons who are employed only when there is a demand for their services to boost production.

Thus, when the economy is booming, Mrs. Okazaki does not have much trouble finding some sort of a job. In the past three years, she has operated a machine stamping simple metal parts, worked as a supermarket cashier, and tried door-to-door sales.

When business slumps, however, she can easily be laid off to cut company costs.

There are now reckoned to be about 5 million women in this category in Japan.

The increasing number of housewives working or seeking work has become one of the most important social trends of the 1980s, as well as an important factor in allowing the Japanese economy to continue in this era of low growth to outperform other industrialized nations.

According to a new government survey, an additional 1.7 million married women have entered the work force in the past three years, and their numbers are likely to continue growing.

In fact, married women now account for one-quarter of the entire labor force and 60 percent of all female workers.

Between 1960 and 1980, the number of women workers doubled. But for female part-time workers, the increase was almost fivefold, according to government statistics.

The prime minister's office reports that in 1981 slightly over 22 percent of such females actually worked the same hours and days as regular employees, while about 50 percent worked more than 35 hours a week.

But government figures on pay show women in regular employment average only 60 percent and part-time female workers 45 percent of comparable male salaries.

''Women part-time workers are holding down the entire Japanese wage scale,'' says Emiko Shibayama, an expert on women's labor issues. This is one reason why Japanese products cost less than comparable American and European ones, she says.

Mrs. Shibayama believes use of part-time women workers is ''part of Japan's international economic strategy for the 1980s,'' pointing out that they - not trained males who command high wages - are the ones who stand in front of machines pushing buttons all day in the current era of office and factory automation.

She says many big manufacturing companies now farm out a sizable percentage of their production processes to small companies using cheap housewife labor. ''In many supermarkets, for example, everyone is now part-time but the manager, '' she adds.

Some analysts say that part-time workers are seen by business managers as a way of side-stepping the high cost and inflexibility of Japan's famous ''lifetime employment system.''

They allow companies to expand and contract at will in tune with the national and international economy without concern for what to do with excess workers who cannot be fired or laid off during hard times.

Many union officials also believe that managements are using housewives as a weapon to break union power.

Such charges don't really concern Noriko Okazaki, who is more concerned with supplementing her meager family income. And she finds part-time work best suited to fit in with her household responsibilities.

A report from the prime minister's office says the strain on household income by a protracted economic recession was the single most important factor in persuading millions of married women to resume working.

Some 61 percent of housewives whose husbands' yearly income is below $9,000 now are employed, compared to 42 percent in cases where the husband earns more than $20,000, according to the report.

''Inflation and higher taxes mean my husband's pay keeps on shrinking,'' Mrs Okazaki lamented during an interview in the family's cramped three-room apartment. ''Also, business hasn't been good, so he doesn't have much overtime and his twice-yearly bonus is also smaller than it used to be,'' she said.

''When the two boys started elementary school, I decided to try and get a job again. It wasn't just out of economic considerations. . . . I was bored sitting at home all day.''

In fact, recent studies have shown a growing determination among Japanese women to achieve a greater measure of economic independence and self-fulfillment than can be realized in their traditional roles as specialists in housekeeping and child rearing.

Ironically, it was easy for Mrs. Okazaki to find work, because she had virtually no academic or professional qualifications. There is considerable evidence that the higher a woman's education, the more difficult it is for her to obtain employment.

Some months ago the union of a major bookseller, Kinokuniya, leaked what it said was a company management document on hiring practices.

To be shunned, the document declared, were short, ugly women; those wearing spectacles; divorcees; those living in rented rooms (whose morals might be suspect); those belonging to political or religious groups; highly educated women (regarded as ''too headstrong''); and the daughters of teachers or writers.

A company spokesman admitted the document was genuine, but said it was ''only for reference'' and had since been ''superseded.''

Almost half of Kinokuniya's work force, however, is part-time, and most of them are women.

According to Mrs. Shibayama, the labor specialist, the attitude revealed by the Kinokuniya document is widespread. ''Only with most firms, it is not so easily pinpointed,'' she said.