PURPOSE: To provide the optical signal receiver capable of controlling optical axis misalignment with good accuracy while realizing high S/N.

CONSTITUTION: A photodetector 3 for signal reception exists at the focus of a reflection mirror 2. A photodetector 4 for detecting optical axis misalignment is equally divided to four photodetecting surfaces 4a to d by a blind zone 7 and a circular hole 8 is formed at its central part. These photodetectors are so installed that the center of the hole 8 aligns to the optical axis of the reflection mirror 2 and that the bore of the hole 8 comes into contact with the flank of a circular cone formed by connecting the outside diameter and focus of the reflection mirror 2 between the photodetector 3 and the reflection mirror 2. The reflection mirror 2 and the photodetection 3 for signal reception and the photodetector 4 for detecting optical axis misalignment are integrated by a supporting means 5. The adjustment of the optical axis is executed by a control means 6 according to the output of the photodetector 4 for detecting optical axis misalignment.