Abstract: The present invention provides a power supply unit of a camera which efficiently drives a heavy-load system even when a power supply voltage is low and thus drives a heavy-load circuit in a short time in the photographing sequence of the camera without any trouble. The power supply unit includes a charging section for charging a capacitor with a boosted DC power supply voltage, a switching section which receives the output voltage of the charging section and the DC power supply voltage and selectively applies one of these voltages to the heavy-load circuit, and a control section for controlling operations of the switching section and the charging section. The control section controls the switching section such that the output voltage of the charging section is output in the early stage of a time period during which the power supply voltage is being applied to the heavy-load circuit and then the DC power supply voltage is output.