There are provided a plastic molded optical element and a molding mold therefor capable of preventing flash generation as well as making the handling of the molded optical element easy by forming a projection on the main body of an optical element, corresponding to the matching portions (parting planes) of the molding members of the molding mold or die members for molding the optical element. A thin projection is formed on the main body of the optical element in a thickness required for securing a required strength in relation to the matching portions (parting planes) of the molding members or die member for molding the optical element.