Provided is a position detection device including a detection unit configured to have a photo-reflector including a light emitter and a light receiver, the light receiver receiving light emitted from the light emitter and reflected by a reflective surface moved in a predetermined direction, the detection unit detecting a movement amount of the reflective surface based on a change in intensity of the received light, and a transparent member configured to be disposed between the reflective surface and the detection unit and to move together with the reflective surface, the transparent member being provided with a light blocking surface configured to block light and a light transmitting surface configured to transmit light, the light blocking surface and the light transmitting surface being arranged in a moving direction of the reflective surface.