PURPOSE: To improve the shrinkage factor of film and its flatness by a method wherein the film is relaxed in the longitudinal direction while being held by clips in the oven of a stenter.

CONSTITUTION: The film 2 is fed into a stenter provided with a joint part 8 for joining together chain links 7 in a mutually bendable manner between the adjacent clips 6 of a clip chain and having connecting members and with a guide rail 14 adapted for engagement with the connecting members to mutually bend the chain links 7. The method for producing the film is characterized by setting the guide rail 14 to the adjusting position to adjust the flexibility of the chain link 7 at each end of the joint part 8, adjusting the relaxing factor of the film 2 in the longitufinal direction by this adjustment of the flexibility and relaxing the film in the longitudinal direction in the stenter.