Provided is an imaging device operated at high speed and low power consumption. The imaging device includes a pixel and a first circuit. The pixel includes a first photoelectric conversion element and a second photoelectric conversion element. The first circuit is configured to compare a first signal which is output from the pixel on the basis of imaging data obtained by the first photosensitive conversion element to a second signal which is output from the pixel on the basis of imaging data obtained by the second photosensitive conversion element for determining whether there is a difference between the first signal and the second signal. Thus, edge detection can be performed without a periphery device for edge detection outside the imaging device.