An output transistor is made to perform switching operation synchronous with a clock signal in a current mode based on an error voltage, which is commensurate with the difference between a feedback voltage commensurate with an output voltage and a reference voltage, and a slope voltage, which is commensurate with a current that passes through the output transistor. Based on the result of comparison of the error voltage with a skip threshold voltage, a skip signal is generated. When the skip signal turns to high level in response to a light load, the switching operation is stopped. Thereafter, when the skip signal turns back to low level, the output transistor is turned on asynchronously with the clock signal.