A semiconductor device providing a control circuit for controlling a switching power supply apparatus includes: an intermittent-oscillation control circuit which outputs an enable signal providing instructions to execute and suspend switching alternately; a turn-on control circuit which changes between an execution state and a suspension state of the switching according to the enable signal, and outputs, only in the execution state, a turn-on signal which turns on the switching element with a switching period; and an intermittent-oscillation frequency control circuit which causes the turn-on control circuit to delay the changing between the execution state and the suspension state so that an intermittence period including periods during which the turn-on control circuit is in the execution state and the turn-on control circuit is in the suspension state falls outside of a specific time range. Intermittent oscillation is thus operated out of a specific frequency band within an audible frequency range.