Abstract: A power supply device for a computer device mainly comprises a DC to DC converter used to receive and convert an outside DC power supply to a variety of DC voltages needed for a computer device and an up/down regulator connected to the DC to DC converter and used to stabilize an output voltage. According to the present invention, the up/down regulator is installed before the +12 voltage input end of the computer device. Whereby, the +12 voltage can be stabilized and the work loss of the power supply for the computer can be lowered down.