A switching booster power circuit includes a power switch, a booster circuit, a switching control, a voltage detector and a delay circuit. The voltage detector detects an input voltage value at a predetermined point of an electricity supply line from the power switch to an electric load, and determines the input voltage value to be larger than a predetermined voltage threshold or not. The delay circuit outputs an enabling signal enabling the switching control to operate, when a predetermined time period is elapsed after the input voltage value becomes larger than the voltage threshold.