To provide a method for producing an optical film by which the optical film suitably usable as a phase difference film or the like, and having excellent optical isotropy is provided by a melt extrusion method by a T-die in high productivity.

The method for producing the optical film comprises taking off the film at 10-100 m/min take-off speed when producing the film by extruding 70-40 wt.% maleimide-olefin copolymer having 1×103-5×106 number average molecular weight, and 30-60 wt.% acrylonitrile-styrene copolymer containing 21-45 wt.% acrylonitrile unit by the melt extrusion method by the T-die, and forming the film on one or more cooling rollers.