Power consumption is reduced. A semiconductor device includes an arithmetic processing circuit, a power supply circuit, a power management unit (PMU), and a power switch. The arithmetic processing circuit includes a storage circuit retaining generated data. The storage circuit includes a backup circuit including a transistor and a capacitor. When a control signal for transition to a resting state is input from the arithmetic processing circuit, the PMU performs voltage scaling operation for lowering a power supply potential of the arithmetic processing circuit. When the period of the resting state exceeds the set time, the PMU performs power gating operation for stopping power supply to the arithmetic processing circuit. Data saving operation of the storage circuit is performed before the voltage scaling operation.