A voltage conversion circuit with reduced power consumption can be used for a power supply device (100). The power supply device (100) is composed of a power supply circuit (3) including an alternating power supply (1) and a rectifying circuit (2); a voltage conversion circuit (6) including a plurality of capacitors (4) and a switching circuit (5); and a load circuit (7). The voltage conversion circuit (6) is connected between the power supply circuit (3) and the load circuit (7). The alternating power supply (1) is connected to a switching circuit (5) of the voltage conversion circuit (6) without having the rectifying circuit (2) in between. An output voltage (potential fluctuation: a potential difference generated in the signal waveform of the power supply voltage) from the alternating power supply (1) prior to rectification is applied to the switching circuit (5). The alternating power supply (1) is also connected to the capacitors (4) through the rectifying circuit (2), and output power after rectification is applied to the capacitors. The voltage conversion circuit (6) supplies the load circuit (7) with the power supply voltage inputted from the power supply circuit (3) by increasing or reducing the voltage.