According to one disclosure, a first semiconductor chip in which a plurality of pixels are formed and a second semiconductor chip stacked on the first semiconductor chip and including analog-to-digital conversion units are provided. A comparator includes a differential amplifier circuit that outputs a first signal, a source ground circuit that includes an input transistor to which the first signal is input and a load transistor cascade-connected to the input transistor and outputs a second signal from a connection node of the input transistor and the load transistor, and a current compensation circuit that includes a current control transistor to which the second signal is input and a current source transistor cascade-connected to the current control transistor and in which the current control transistor causes a second current to flow that changes complementarily with respect to a change of a first current flowing in the source ground circuit.