A semiconductor laser device is mounted on the side of one end surface on lead frame in a recess of an insulating molding member, a three-beam generating diffraction grating is disposed in the center, and a transmission type holographic optical element is disposed on the side of the other end surface. After a flexible circuit board is fixed to the lower surfaces of leads and the lead frame, a photodiode for a signal detection is mounted on the surface of the flexible circuit board, and is so folded upward as to be perpendicular to the upper surface of the lead frame. The insulating molding member is mounted on the one end surface of the insulating molding member through a circular screw through a hole and an elliptic screw through a hole by screws.