Sadaharu Oh, the king of Japanese baseball, belted his 756th home run tonight to top the record held by America's Henry Aaron, rousing his adoring country to a peak of exultation.

Oh, a national hero for years in this baseball-mad country, slugged a high line drive deep into the right-field stands of Tokyo's Korakuen Stadium.

The blow, struck in the third inning off a 3-2 pitch, permitted his ecstatic fans who had suffered through weeks of anticipation, to proclaim him the world's leading home-run hitter.

That title is disputed in the United States and even in sober baseball circles, here, where it is pointed out that hitting home runs is easier in Japan than in the American big leagues.

Oh plays in parks smaller than American stadiums - it is barely 300 feet down the line in Japan. And experts agree that Japanese pitchers lack the power and sophistication of those in the United States.

But all of that was irrelevant nitpicking tonight in Japan where wild celebrations broke out in bars, restaurants and homes. In the stadium, 55,000 fans cheered, threw confetti, and shouted "Banzai" (a kind of Japanese "hooray") for 10 minutes after the ball had landed. Oh's parents sat in the stands weeping with relief and joy.

In a business section of Tokyo, the windows of an office building were lighted in a pattern that declared: "Congratulations Oh 756." A sober wedding dinner was interrupted with applause when one celebrant picked up the news on his transistor radio.

The happiest man in the stadium was Miyoshi Furuya, 25, who scrambled after the ball from his seat in the right-field stands where he had bought tickets for five consecutive nights. Furuya emerged dusty from the mob to tell television interviewers that, "Even if I die, I will not drop the ball, never, never."

The unhappiest was Yashuhiro Suzuki, the pitcher for the Yakult Swallows who served up the wrong pitch and them watched Oh circle the bases. As a kind of national joke, an airline had offered a free excursion to the island of Saipan - where thousands of Japanese soldiers committed suicide in World War II - to the pitcher who allowed Oh to break the record. But for the game, Suzuki had jocked, "I will go to Saipan Island." But after the game, he angrily told reporters: "No - never."

The baseball tension had been mounting in Japan all summer as Oh, a 19-year veteran with the Yomiuri Giants, neared Aaron's record. People have been glued to their television sets and radios in offices, taxis, bars and homes and all recent Giant games have been sold out.

Some workers have enjoyed what they happily call "the Oh shift" - they were allowed to go home early to get in front of their television sets.

The tension even penetrated te pachinko parlors where Japanese play their form of pinball in a state of dazed concentration. Some parlor owners fitted small television sets into the gameboards so that players could watch the baseball games along with the whirling steel balls.

It all come to a climax tonight as Oh stepped to the plate in the third with one man on. With the count at 3 and 2, Oh reared back in his so-called "flamingo" stance - his right foot raised off the ground in the style once made popular by the American slugger Mel Ott. He walloped the ball 328 feet into the salute, raised both arms in a victory salute, and jogged slowly around the bases.

Later, the stadium lights were turned off and Oh stood in spotlights alone on the mound to thank his fans. He said that for the last several days, "I felt directly on my skin your passion. All of you helped my dream to come true. I will swing the bat as long as my body allows."

Aaron, who hit his 755th homer July 20, 1976, expressed his admiration for Oh's skill, the Associated Press reported.

["I would have loved to have been there tonight to put the crown on top of his head because he certainly is quite a gentleman and the people of Japan have a lot to be proud of," he said in a videotape message braodcast by Japanese television. Aaron, who played for the Atlanta Braves and Milwaukee Brewers, retired last year and now is a vice president with the Braves.]

["I want to wish (Oh) the best of luck in the world," said Aaron. "I know he's capable of hitting a lot more home runs.]

The 37-year-old first baseman hit the record-breaker on the 7,878th trip to the plate of his career. Aaron had batted 12,364 times when he hit his 756th homer. Oh has played in 19 seasons, compared to Aaron's 23.Statisticians calculate that Oh has hit a homer once in every 10.4 trips to the plate compared to once in every 16.2 for Aaron.