An imaging device with high imaging quality capable of being manufactured at low cost is provided. The imaging device includes a first transistor, a second transistor, a third transistor, a fourth transistor, a photodiode, and a capacitor. Each of the first to the fourth transistors includes a first gate electrode and a second gate electrode, and the second gate electrode of each of the first to the fourth transistors and one electrode of the capacitor are electrically connected to an anode electrode of the photodiode.