PURPOSE: To obtain a melt-moldable aromatic polyester resin excellent in heat resistance and mechanical properties, containing four specified kinds of structural units at a specified ratio.

CONSTITUTION: An aromatic polyester resin containing at least 95mol.%, based on the total structural units, structural units of formulas I, II, III and IV and containing 16W19mol.%, based on the total structural units, structural units of formula I. The total of structural units of formulas II, III and IV amounts to 81W84mol.% of this polyester, and the molar ratio of the structural units of formula II to the structural units of formulas II, III and IV is 9W1. If this ratio is above 9, the bending strength and impact strength of the formed polyester are markedly decreased, and if this ratio is below 1, the m.p. of the formed polyester is so high that its melt polymerization is difficult and only a polymer of low MW one can be obtained. Although the formation of the polyester from monomers is preferably carried out by melt polymerization or slurry suspension polymerization in a medium, melt polymerization is particularly preferable.