An optical module comprises a first optical block and a second optical block that are positioned in relation to and fixed to each other and each have lenses that are to have the optical axes thereof aligned, and has stepwise positioning means. A first-step positioning means has a visible shape. A second-step positioning means comprises edges and spring pieces that each have an abutment slope. Four spring pieces are formed on the second optical block so that the abutment slopes thereof are positioned at the four corners of the second optical block. The two abutment slopes on one end side in the longitudinal direction are mirror images of each other. Each of the abutment slopes on the other end side is positioned on the same plane as the abutment slope reached through extension in the longitudinal direction. Each abutment slope is positioned through abutment with an edge of the first optical block. A third-step positioning means comprises a recess and a guide slope formed on one of the two optical blocks and a protrusion formed on the other optical block. The protrusion can be engaged with the recess.