Disclosed is a retardation film using a polyester having a photoelastic coefficient of from -40 10<-12> Pa<-1> to 40 10<-12> Pa<-1>. Also disclosed is a polyester resin for optical use which contains a phosphorus compound while having an alicyclic component and a fluorene derivative component as constitutional units. This polyester resin for optical use satisfies the following formulae (6) and (7). 100 DEG C = glass transition temperature = 150 DEG C (6) 1.0 = (Ma/2 + Mb + Mc)/P = 5.0 (7) (In the formulae, Ma represents the mole number of alkali metal elements contained in 1 ton of the polyester resin; Mb represents the mole number of alkaline earth metal elements contained in 1 ton of the polyester resin; Mc represents the sum of respective mole numbers of Zn, Co and Mn metal elements contained in 1 ton of the polyester resin; and P represents the mole number of phosphorus element contained in 1 ton of the polyester resin.