A photodetector including: a case including a light receiving surface provided on an upper surface and having a first region that transmits visible light and a second region that transmits less visible light than the first region; a printed circuit board provided to face the light receiving surface; and a plurality of electronic components provided on a light receiving surface side of the printed circuit board and including a first light receiving element configured to detect visible light. The first light receiving element is disposed at a first position of the printed circuit board exposed to the visible light transmitted through the first region. The number of mounted electronic components disposed at the first position is smaller than the number of mounted electronic components disposed at a second position of the printed circuit board other than the first position.