To prevent a planar failure by the adhesion of dust, a defective bright spot in a polarizer, and bedewing in a drying process.

A film producing apparatus 10 is installed in a clean room 34 and constituted of a casting/peeling process part 12, a tenter drying process par 14, a roll drying process part 16, and a winding process part 18. Each process part is respectively installed in a casting/peeling chamber 42, a tenter drying chamber 44, a roll drying chamber 46, and a winding chamber 48. The winding chamber 48 is controlled so that the difference of the internal pressure to an external pressure is -5 to 15 Pa.