A LDO and a switching regulator are connected in parallel with each other. The power supply device selects and actuates either of the LDO or the switching regulator in accordance with a switching signal from the outside. When making the switch from the LDO to the switching regulator so as to be actuated, the power supply device causes operation periods of the LDO and the switching regulator to overlap each other. At least during the period in which the operation periods overlap each other, the power supply device makes current drive performance of a synchronous rectification transistor of the switching regulator lower and makes the same return to a normal state after the LDO stops its operation.