Biography; The man who made 'Star Wars'; Skywalking, by Dale Pollock. New York: Harmony Books. 304 pp. $14.95.

''Skywalking'' is the word for it, all right. Still a young man, filmmaker George Lucas measures his fortune in tens of millions - much of it raked in by hero Luke Skywalker, whose ''Star Wars'' adventures have become a pop-culture mainstay.

Other cornerstones of the Lucas empire include ''Raiders of the Lost Ark'' and ''American Graffiti,'' two more of the biggest hits ever. Resting on these foundations is the fabulous financial edifice of Lucasfilm Ltd., pulling in still more loot from merchandising deals and investments.

Added up, it's a good definition of the American dream: show biz at its showiest, big money at its biggest. And all sprung from the impish dreams of a boy wonder who believes in hard work, simple ideas, old-fashioned storytelling.

The irony is that Lucas dislikes making movies. A shy person, gifted at the editing table but anxious with people, he shivers at the thought of a Hollywood set with swarms of employees and countless daily decisions. He enjoys dreaming films up and tinkering with technical aspects. But actually directing them? He'd rather leave that to hired hands.

This love-hate relationship with filmmaking is just one of the unlikely twists in Dale Pollock's enlightening biography. Pollock regards Lucas as emblematic of all the young ''movie brats'' who have taken over a large chunk of the American cinema scene. But it soon becomes clear that Lucas is one of a kind , wrapped in enigmas like these:

* Though seen by admirers as a one-man hit factory, he has directed only three movies and produced four. In each category his first effort was a flop.

* Though he is credited with great filmmaking savvy, his pictures have been beset with troubles. The special-effects crew for ''Star Wars'' destroyed whole sets with overzealous explosions. ''The Empire Strikes Back'' ran out of money weeks before completion. ''American Graffiti'' was almost shelved by studio executives who thought it confused and trivial.

* Though admired for his storytelling talent, Lucas is uncomfortable with words; like Henry Ford, he can't write more than a few lines without spelling errors or worse. Scriptwriting drives him to distraction - while working on ''Star Wars,'' he snipped off bits of his hair when the right words wouldn't come. Yet he sticks at it, earning a writing credit on most of his major films.

* Though he belongs to a notoriously fast-living profession, he has dodged every bad habit and led a quiet, home-oriented existence. One of the most successful men ever spawned by Hollywood, he despises it and refuses to live there, partly because of the ''temptations'' he's convinced it would dangle before him.

In sum, Lucas is an unlikely choice for king of the movie world. He says his success ''isn't his fault'' and tries to keep it in perspective. Yet things have a way of growing when he's around. Intended as a modest pastiche on cheap matinee serials, ''Raiders of the Lost Ark'' somehow ended up a big-budget extravaganza.

Like the Empire in a ''Star Wars'' yarn, the big time keeps catching up with our hero - whose latest escape hatch is Skywalker Ranch, a utopian think-tank he's building for filmmakers equally fed up with the competitive mainstream.

After detailing Lucas's unremarkable early years, Pollock traces his life and career through all his films, including the new ''Return of the Jedi.'' The biographer takes his subject with lots of salt, but shows plenty to like and respect in this influential media wizard.