A charging circuit includes a charge pump circuit, an integrating circuit, and a clock signal output circuit. The charge pump circuit generates a boosted voltage by boosting an input voltage at a rate in synchronization with an input clock signal. The integrating circuit is configured to integrate the boosted voltage to apply the integrated boosted voltage to a boost capacitor. The clock signal output circuit is configured to output a second clock signal that is higher in frequency than a first clock signal to the charge pump circuit as the clock signal for a predetermined period of time upon start up, and thereafter output the first clock signal to the charge pump circuit as the clock signal.