A polyester polymer is a condensation product of a diol component and a dicarboxylic acid component, and the diol component (i) includes at least one tricyclonull5.2.1.02,6nulldecanedimethanol represented by the following formula (1): 1 wherein two hydroxymethyl groups are bound to carbon atoms constituting tricyclonull5.2.1.02,6nulldecane ring and wherein each of carbon atoms constituting the ring may have at least one additional substituent; or (ii) the dicarboxylic acid component includes at least one tricyclonull5.2.1.02,6nulldecanedicarboxylic acid represented by the following formula (2): 2 wherein two carboxyl groups are bound to carbon atoms constituting tricyclonull5.2.1.02,6nulldecane ring and wherein each of carbon atoms constituting the ring may have at least one additional substituent. The polyester polymer has an excellent formability in addition to a high heat resistance, low water absorption property, and satisfactory optical characteristics.