An imaging device includes a pixel; a digital circuit; and an analog processing circuit including a constant current circuit, a current comparison circuit, and a control circuit. The pixel is capable of outputting differential data. The constant current circuit is capable of supplying a first current corresponding to the differential data, in accordance with a first control signal. The current comparison circuit is capable of supplying a second current that flows through the constant current circuit in accordance with a change in the differential data. The current comparison circuit has a function of setting a determination signal active depending on whether to supply the second current to the constant current circuit. The control circuit has a function of controlling the constant current circuit and the current comparison circuit to stop their functions as the determination signal becomes active. The digital circuit operates as the determination signal becomes active.