Abstract: In order to realize a photoelectric conversion device having a photoelectric conversion element for outputting a signal according to the incidence of a photon that has a low power consumption, the photoelectric conversion device includes: at least one pixel including a photoelectric conversion element that outputs a signal according to an incident photon; a photon counter that measures the number of photons incident to the pixel; a time counter that measures a time until the photon counter reaches a first threshold after starting measurement and outputs the measured time as a pixel value; and a first threshold changing unit configured to change the first threshold.