An optical film having a thickness of from 10 to 45 μm and containing a cellulose ester and a polyester having a recurring unit represented by the formula 1 and having a terminal blocked with an alicyclic structure wherein Re and Rth are from −5 to 5 nm at a wavelength of 590 nm can be used as an polarizing plate protective film and is capable of ensuring excellent film surface smoothness and the durability of a polarizer under a high temperature and high humidity environment. X represents an acyclic divalent linking group, R represents an alkyl, alkenyl, alkynyl or aryl group, and m represents an integer of from 0 to 4.
