The disclosed photoelectric conversion device includes a photoelectric conversion unit outputting a pulse signal in response to an incident of photon, a signal processing unit that is connected to the photoelectric conversion unit and counts the pulse signal, and a control unit that controls the signal processing unit. The signal processing unit includes a first count processing unit and a second count processing unit arranged in parallel. The control unit is configured to set an active period and an inactive period for each of the first count processing unit and the second count processing unit. A period during which the first count processing unit is active includes a first period during which the second count processing unit is active and a second period during which the second count processing unit is inactive.