To downsize a constant current power supply device that can ensure stability of a constant current output with respect to an input voltage change while satisfying high frequency regulation.

A constant current power supply device 1 includes: a constant current circuit 20 to output a constant current; and a control part 10 to control the constant current circuit 20. The constant current power supply device 1 also includes a power factor improvement circuit 30 disposed closer to an input side of the constant current power supply device 1 than the constant current circuit 20. The power factor improvement circuit 30 is operated on the basis of a gate signal transmitted from the control part 10 to the constant current circuit 20.