An imaging device includes a first substrate and a second substrate stacked thereon. The first substrate includes: a photoelectric converter that converts incident light into a signal charge; a first transistor that outputs a signal corresponding to the signal charge, a gate of the first transistor being connected to the photoelectric converter; and a second transistor, one of a source and a drain thereof being connected to the photoelectric converter, the other of the source and the drain thereof being connected to a source or a drain of the first transistor. The second substrate includes: a constant current source circuit that is connected to one of the source and the drain of the first transistor; and a bias circuit that is connected to the other of the source and the drain of the first transistor and that generates a first voltage and a second voltage different therefrom.