A microcontroller including: a first voltage detection circuit that generates a first detection signal when a power supply voltage decreases to a voltage lower than a first voltage value; a second voltage detection circuit that generates a second detection signal when the power supply voltage decreases to a voltage lower than a second voltage value that is smaller than the first voltage value; a CPU that has a function of switching between a normal operation mode and a standby mode, performs an interrupt processing operation to shift from the normal operation mode to the standby mode when the first detection signal is generated, and shifts to the standby mode independently of the interrupt processing operation when the second detection signal is generated; and a first memory circuit that stores information indicating that the CPU has shifted to the standby mode before completing the interrupt processing operation.