The photosensor includes an APD that has a multiplication region including a photoelectric converter and includes a first capacitor connected to the multiplication region in parallel, and a first transistor connected between the APD and a first power supply (voltage VC). The first transistor applies a reverse bias of a power supply voltage (VC-VA), which is larger than a breakdown voltage VBD, between an anode and a cathode of the APD during a bias setting period by connecting the APD to the first power supply, and stops an avalanche multiplication phenomenon during a light exposing period by disconnecting the APD from the first power supply to accumulate charges generated by the avalanche multiplication phenomenon in the first capacitor.