A control apparatus performs peak current mode control in which a drive switch is turned off when output of a comparator is inverted during an on-operation period determined by a basic signal. The comparator inverts the output when a reactor current increases to a command current. The control apparatus determines that a switching frequency of the drive switch is required to be switched when the output of the comparator is detected to have not become inverted during the single switching period while the peak current mode control is being performed. The control apparatus sets the switching frequency to a first frequency when the switching determining unit determines that the switching frequency is not required to be switched, and switches the switching frequency from the first frequency to a second frequency lower than the first frequency when the switching determining unit determines that the switching frequency is required to be switched.