A method for manufacturing a semiconductor photodetector includes: forming an insulating film on a semiconductor substrate; forming an electrode on and in contact with a predetermined area of a surface of the semiconductor substrate; forming a resist on the insulating film after forming the electrode; forming a power supply layer of a metal on the resist and the electrode; plating a surface of a portion of the power supply layer with a metal coating, after forming the power supply layer, the portion overlying and being in contact with the electrode; after the plating, etching and removing a part of the power supply layer leaving a portion that is covered with the metal coating and is an extension of the electrode; and removing the resist after etching the power supply layer.