To provide an inexpensive optical film excellent in optical homogeneity.

The optical film includes at least one layer based on a crystalline propylene-1-butene random copolymer comprising 70-97.5 mol% of a monomeric unit derived from propylene and 2.5-30 mol% of a monomeric unit derived from 1-butene, wherein the sum total of the monomeric unit derived from propylene and the monomeric unit derived from 1-butene in the crystalline propylene-1-butene random copolymer is 100%. The optical film is formed through stretching in at least one direction. The optical film is a retardation film.