A DC-DC converter is provided with a control circuit 6 which comprises a drive signal generator 11 for producing on-off signals to a control terminal of a MOS-FET 3 in synchronization with pulse signals V.sub.OSC from an oscillator 10; an intermittent controller 12 for producing a control signal V.sub.C1 to drive signal generator 11 in response to the level of detection signal from an output voltage detector 5 to convert MOS-FET 3 to the intermittent operation during the light load period; and a power control circuit 16 for ceasing power supply V.sub.CC to oscillator 10 in response to control signal V.sub.C1 from intermittent controller 12 to stop production of pulse signal V.sub.OSC from oscillator 10 for the cessation term of MOS-FET 3 during the intermittent operation.