A flange portion of this semiconductor laser element is press-fitted, with a front face of the semiconductor laser element serving as the leading head, into an externally-contacting hole portion of a through-hole in a vertical wall portion. The externally-contacting hole portion contacts an outer peripheral surface of the flange portion. A collimator lens is mounted to a support body before or after the flange portion is press-fitted into the externally-contacting hole portion. The press-fitting of the flange portion into the externally-contacting hole portion is stopped at a position where an edge portion, of the flange portion, on the front face side of the semiconductor laser element rests within the externally-contacting hole portion. The collimator lens is mounted to the support body in a path of emitted light in front of the semiconductor laser element.