Signatories of the petition include French New Wave director Jean-Luc Godard, French actor-director Mathieu Amalric and Cannes best director laureate Bernard Tavernier.
The petition is posted on a Web site overseen by French philosopher Bernard-Henri Levy.
Polanski is under house arrest in Geneva in a 33-year-old sex case.
He pleaded guilty in 1978 to unlawful sexual intercourse with a 13-year-old girl. But after a judge said he would renege on the plea bargain, Polanski fled to his native France. He has been a fugitive since then.