Abstract: A dope including a polymer and a solvent is discharged from a casting die (30) to a casting drum (31) while forming a casting bead (38). An upstream side (38a) area of the casting bead (38) is decompressed by a decompression chamber (36) to (atmospheric pressure—300)Pa. Air shielding plates (70, 71) are provided inside the decompression chamber (36). Openings (90) are respectively formed in upper half portions of the air shielding plates (70, 71). A distance L (mm) between a contact position A of the casting bead (38) and the air shielding plate (70) is set in the range of 20 mm to 100 mm. After the casting bead (38) forms a casting film (39) on the casting drum (31), the casting film (39) is peeled and dried to obtain a TAC film.