A power supply device having zero switching voltage is disclosed to include a first switch having a parasitic body diode, a first capacitor, an inductor, a transformer, a second switch having a parasitic body diode, a second capacitor, a first voltage output unit providing a first voltage output, and a second voltage output unit having a third switch and providing a second voltage output. By means of controlling the order in which the first switch, the second switch and the third switch are to be switched on, switching voltage is eliminated from the first switch and the second switch and the working efficiency of the power supply device is raised.