Abstract: This invention relates to processes for producing an olefin-terminated polyester. In one of the processes which comprises reacting an olefin-terminated diester compound with a lactone in the presence of a polymerization catalyst with transesterification ability, the lactone is in a limited amount added to the reaction system. In another process which comprises reacting an olefin-terminated diester compound, a lactone compound, a cyclic acid anhydride and an epoxy compound in the presence of a polymerization catalyst with transesterification ability, the lactone, cyclic acid anhydride and epoxy compound are each in a limited amount added to the reaction system. In accordance with this invention, olefin-terminated polyesters having high terminal modification rates can be synthesized.