In a direct-current power supply device that includes a smoothing capacitor C1, which performs a DC/DC converter operation, a transformer T1, a switching element Q1, a diode D2, a smoothing capacitor C2, a reactor L1, which performs a PFC operation, a fast recovery diode D1 and a switching element Q1, when compared with the case of a rated load, the voltage of the smoothing capacitor C1 of a PFC circuit rises at a time when a load is light. Therefore, the following has been required: a capacitor having a sufficient withstanding voltage rating, or an operation of connecting a plurality of capacitors in series or any other operation to secure a voltage-withstanding capability.A direct-current power supply device 1, in which a switching element Q1 used by a PFC circuit is shared as a switching element Q1 by a DC/DC converter, includes voltage suppression means (switching elements Q2 and Q3 and resistance R2) for supplying electric charge accumulated in a smoothing capacitor C1 to a power supply Vcc of a control circuit CTL1 that controls the switching element Q1 at a time when a load is light in order to suppress a rise in voltage in the smoothing capacitor C1.