To provide a small-loss power supply device which has no influence on the operation of a circuit by limiting rush current by means of a resistor for liming current which is serially connected to a capacitor at the time of turning the power on and shorting the resistor for limiting current in the steady state.

A parallel circuit of a resistor R1 and a transistor Q1 is serially connected to an input capacitor C1 and the gate voltage of the transistor Q1 is supplied by a parallel circuit of a resistor R2 for dividing input voltage and a resistor R3 and a capacitor C2. At that time, a time constant determined by the resistors R2, R3 and the capacitor C2 is set larger than the one determined by the input capacitor C1 and the resistor R1. By this method, the transistor Q1 starts conducting after charging of the capacitor C1 is finished.