When a boosting operation stops, it is ensured that a boosting switching regulator does not output an output voltage. When a high signal is applied to the gate of a PMOS transistor Q1 to turn off the transistor Q1, a higher voltage of an input voltage VDD and an output voltage VOUT is supplied to a buffer 171 as a supply voltage, and the higher voltage is applied to the gate of the transistor Q1 by the buffer 171. As a result, the transistor Q1 can be surely turned off. Hence, when the boosting operation by the boosting switching regulator stops, the transistor Q1 that outputs the output voltage VOUT can be surely turned off. Also because the voltage based on the input voltage VDD is applied to the back gate of the transistor Q1 by the switch 3, the parasitic bipolar transistor caused by the transistor Q1 is not turned on.