His company, Lucasfilm, said the first Star Wars prequel, which was hugely hyped, "didn't live up to expectations".
Many Star Wars fans were disappointed by the film, saying its plot was weak and there were too many computer effects.
And Ewan McGregor, who starred as the young Obi Wan Kenobi in Episode I, said the film was "disappointing" and "flat".
Better next time
Lucasfilm promises the new adventure, Attack Of The Clones, will be much better.
It'll have a "darker feel" and "no silly characters or kids."
Attack of the Clones opens worldwide on 16 May.