Abstract: A dope is prepared from TAC, solvent and the like. The dope is cast from a casting die (31) onto a belt (34) to form a casting film (69). The casting film (69) is peeled as a wet film (74) from the belt (34). The wet film (74) is transported to a tenter device (35), in which both side edge portions are clipped by tenter clips (100). The content of the remaining solvent in the wet film 74 is determined to 100 wt. % on dry basis. The tenter clips (100) (temperature, 40° C.) has a support surface (100a) for supporting the side edge portion of the wet film 74 thereon. A surface tension of the support surface (100a) is 3.1×10?2 N/m, a surface roughness Ra of the support surface (100a) is 0.3 ?m, and a surface hardness of the holding surface (100a) is 700 Hv. Therefore, the adhesion of the foreign materials is reduced. The wet film (74) is dried with stretching in the widthwise direction by the tenter device (35), so as to obtain a TAC film (82).