Disclosed is a switching constant-current power supply system, comprising a feedback circuit 7 provided between a detector circuit 5 for generating a first feedback signal in proportion to a current flowing in a load 6, and a control circuit 4 for driving a first power converter circuit 3 which is provided on the input side of a second power converter circuit 10 to stabilize the load current. The feedback circuit 7 includes a signal hold section 8 for generating a second feedback signal. The feedback circuit 7 is operable to supply the first feedback signal to the control circuit 4 in a current supply period, and to supply the second feedback signal to the control circuit 4 in a current cutoff period. The second feedback signal has a signal value approximately equal to that of the first feedback signal appearing in the current supply period. The switching constant-current power supply system can stabilize the load current even under the condition that the load is repeatedly turned on/off.