An imaging device includes a plurality of pixels each including a plurality of avalanche photodiodes, a setting unit configured to set the plurality of avalanche photodiodes to an active state or an inactive state separately, and a counter circuit that counts and outputs number of photons determined by the avalanche photodiode(s) set to the active state out of the plurality of avalanche photodiodes, wherein the imaging device is configured to change the number of avalanche photodiodes set to the active state out of the plurality of avalanche photodiodes in accordance with brightness of an object.