A power supply apparatus for a light source of an endoscope includes a light source unit including an input portion that a control signal is input from an output control unit, the light source unit switching a brightness of the illumination light by the control signal and a control signal cable connected to the output control unit and the input portion, and including a current control signal line to transmit the control signal, and a GND line. The power supply apparatus for a light source of an endoscope further includes a common-mode rejecting portion provided in the input portion, connected to the control signal cable, and rejects noise superimposed on the control signal cable.
