Method of manufacturing optical element made of glass

An optical element manufacturing method has a preparation step of preparing a lower mold and an upper mold. The lower mold has an outer shape restricting surface for the optical element. A reference surface formation step of forms a positioning reference surface on a rim of the optical element by heating the outer shape restricting surface of the lower mold and dropping molten glass onto the lower mold surface so as to collide with the lower mold surface and spread to be in contact with the outer shape restricting surface. A pressing step forms the two opposed optical function surfaces of the optical element by pressing the glass. A temperature of the outer shape restricting surface in the reference surface formation step and the pressing step is higher than a temperature which is 100° C. less than a glass transition temperature (° C.) of the glass.