The present invention relates to an optical film produced by stretching a film having a low residual solvent amount in a machine direction followed by heat-treating it at a temperature falling from the glass transition point (Tg) to the melting point (Tm) thereof, which is a cellulose acylate film satisfying the following relations (1) to (6) and containing at least one cellulose acylate and at least one retardation enhancer having an absorption maximum wavelength λmax of from 280 nm to 380 nm: (1) 35 nm≦Re(550)≦75 nm, (2) 85 nm≦Rth(550)≦140 nm, (3) 0 nm