PURPOSE: To prevent the misregistration of a photodetector by soldering the terminals of the photodetector to a supporting member and flexible printed circuit while the photodetector is held positioned on a mounting window of the supporting member consisting of the same material as the material of a housing.

CONSTITUTION: The flexible printed circuit 6 formed with signal wirings is mounted on the supporting member 7 which is formed with the mounting window 7a of the photodetector 5 and mounting terminals 7b to 7g and consists of the same material as the material of the housing 10 of an optical pickup device. The terminals 5a to 5f of the photodetector 5 are soldered to the supporting member 7 and the flexible printed circuit 6 while the photodetector 5 is held positioned to the window 7a and thereafter, the supporting member 7 is mounted on the housing 10 of the optical pickup device in such a manner that the supporting member comes into contact with the flexible printed circuit 6 on the surface opposite to the mounting surface thereof. This supporting member 7 and the housing 10 of the optical pickup device consists of the same material and the generation of a dimensional error in the mounting part of the photodetector 5 is obviated. The deviation in the mounting position of the photodetector 5 is obviated in this way.