To provide a memory device with short overhead time and a semiconductor device including the memory device. A memory device includes a first circuit that can retain data and a second circuit by the supply of power supply voltage. The second circuit includes a third circuit that selects a first potential corresponding to the data or a second potential supplied to a first wiring; a first transistor having a channel formation region in an oxide semiconductor film; a capacitor that hold the first potential or the second potential that is selected by the third circuit and supplied through the first transistor; and a second transistor controlling a conduction state between the first circuit and a second wiring that can supply a third potential in accordance with the potential retained in the capacitor.