The present invention resolves a problem that occurs to a film which is being washed. A film production method of the present invention includes the steps of: (i) passing a heat-resistant separator above rollers located above a washing tank; (ii) lowering another roller into water through a space between the rollers; and (iii) moving at least one of the rollers and the another roller so as to increase a surface area by which the heat-resistant separator is in contact with the another roller.