A polyester has excellent thermostability with only a small reduction in intrinsic viscosity during melt molding. The polyester is obtained from a dicarboxylic acid, and/or an ester-forming derivative thereof, and an ethylene glycol, a catalyst selected from the group consisting of a titanium compound, aluminum compound and antimony compound, a phosphorous compound selected from the group consisting of phosphoric acid, trimethyl phosphate, ethyl diethylphosphonoacetate, 3,9-bis(2,6-di-t-butyl-4-methylphenoxy) -2,4,8, 10-tetraoxa-3,9-diphosphaspiro[5,5]undecane and tetrakis(2,4-di-t-butyl-5-methylphenyl) [1,1-biphenyl]-4,4′-diylbisphosphonite, wherein the polyester contains 15 to 203 ppm of a sum of copolymerized 1,2-propanediol and/or uncopolymerized 1,2-propanediol wherein ethylene glycol is obtained from biomass and has content of 1,2-propanediol of 45 to 1000 ppm.