To provide a method of manufacturing a cellulose acylate film which has large Re and cannot be easily broken, and in which there are not galvanized sheet plate-like wrinkles, the humidity change of Re is small, and the product width is wide.

The method of manufacturing a cellulose acylate film includes: previously stretching the cellulose acylate film; and thereafter heat-treatment at temperature T satisfying TcTTm0, inhibiting the dimensional change in a direction perpendicularly intersecting with the direction of the previously stretch. In addition, Tc and Tm0 respectively express the crystallization temperature and the melting point of the cellulose acylate film before the heat treating.