To comprehensively improve defects in appearance accompanying the increase in the speed of a film forming process.

A dope is prepared by dissolving in an organic solvent a cellulose acylate satiffying the following conditions: the degree of substitution of hydroxyl group in the cellulose conforms to 1.5≤A+B≤3.0, 2.0≤A≤3.0 and 0≤B≤1.0, wherein A and B represent acyl groups substituted for hydroxyl groups in the cellulose with A standing for the degree of substitution by the acetyl group and B standing for the degree of substitution by the acyl group having 3 to 22 carbon atoms. The dope is cast from a casting die 15 onto an endless belt 14 revolving within a casing 11, and dried to form a film 24. A wind pressure pulsation in the casing 11 is suppressed by installing a pulse absorption chamber 20 in the casing 11. A bead pulsation is suppressed; by arranging labyrinths 16, 17 and a seal at least in one side, front or rear, of a casting section A, and by depressurizing, from backside, a ribbon made of beads delivered from the casting die 15.