A method of manufacturing an optical element module in which an optical element and a semiconductor circuit element are mounted on one surface of a silicon substrate, a mirror surface inclined at approximately 45 degrees is formed on the other surface, and an optical fiber facing the mirror surface is disposed in a V groove formed along the other surface, the method of manufacturing includes the steps of forming the mirror surface and V-shaped side surfaces of the V groove simultaneously by first crystal anisotropic etching on the other surface, and forming an attaching surface substantially perpendicular to the one surface and the other surface, which is formed at an end side of the V groove, and for attaching an end of the optical fiber, by second crystal anisotropic etching in a crystal plane orientation different from that of the first crystal anisotropic etching.