To provide a production method of a phase difference film enabling to stably produce the phase difference film, which has an uniform retardation value and generates no color irregularity in a liq. crystal display device by making a tensile force uniform, which is applied to a thermoplastic resin film in stretching, over the total film width.

When a phase difference film is produced from a thermoplastic resin film, which is produced by solution cast method and contains solvent of 0.5-3.0 wt.%, in a phase difference film production apparatus provided with a pre-heating zone and a stretching zone, the production method of the phase difference film is characterized in that the thermoplastic resin film is preheated so as to be at temp. of (Tg-25°C) to (Tg-15°C) [where, Tg is a glass transition temp. of the thermoplastic resin film (°C)] in the preheating zone, and is stretched at a temp. of Tg to (Tg+20°C) in the stretching zone.