A voltage measuring apparatus electrically connected to buck circuits includes the same number of RC circuits as there are buck circuits, an analog/digital (A/D) convertor, a controller, and a display unit. Each RC circuit is configured to be electrically connected in parallel with an inductor of one corresponding buck circuit. The A/D convertor selectively obtains an analog voltage of one of the buck circuits, and converts the analog voltage signal into a digital voltage signal. The controller controls the A/D convertor and receives the digital voltage signal from the A/D convertor. The display unit displays a decimal voltage value based on the digital voltage signal.