[PROBLEMS] To downsize a photodetector-mounted apparatus. [MEANS OF SOLVING THE PROBLEMS] A photodiode (6) that generates an electric signal according to light reception onto a light receiving surface (6a) is attached to a small printed board (10). An electromagnetic shield cover (14) formed separately from the photodiode (6) is disposed in front of it, and is mounted on the small printed board (10). The electromagnetic shield cover (14) is provided integrally with a substrate fixing portion (14d) fixed to a substrate (2), and forms a specified angle with respect to the substrate fixing portion (14d). In addition, the substrate fixing portion (14d) is mounted to the substrate (2) while kept in contact with the substrate (2).