Niu, known for Taiwanese blockbusters “Monga” and “Love”, denied the allegations, claiming that he “made a mistake but didn’t commit a crime”.
He has yet to comment on the ruling, which he can appeal, and remains free for now.
When the allegations first surfaced Niu told reporters he hoped for a fair hearing but feared public sentiment had made up its mind.
“There is another public trial going on now and I have already been handed a death sentence,” he said.
Taiwan has a vibrant film industry and hosts the annual Golden Horse Awards — dubbed the Chinese-language Oscars.
The #MeToo movement sparked by assault and rape allegations against convicted Hollywood mogul Harvey Weinstein has led to similar abuse being exposed in industries across the world.
But the movement has so far had little impact in Taiwan.