To provide an imaging device capable of high-speed reading. The imaging device includes a photodiode, a first transistor, a second transistor, a third transistor, and a fourth transistor. The back gate electrode of the first transistor is electrically connected to a wiring that can supply a potential higher than a source potential of the first transistor and a potential lower than the source potential of the first transistor. The back gate electrode of the second transistor is electrically connected to a wiring that can supply a potential higher than a source potential of the second transistor. The back gate electrode of the third transistor is electrically connected to a wiring that can supply a potential higher than a source potential of the third transistor and a potential lower than the source potential of the third transistor.