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 for 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 to the PMU, the PMU performs voltage scaling operation for lowering the power supply potential of the arithmetic processing circuit. When the time of the voltage scaling operation is longer than the time of the resting state, the PMU performs power gating operation for stopping supply of power to the arithmetic processing circuit. The storage circuit performs data backup operation before the PMU performs the voltage scaling operation.