The endoscope beam source apparatus includes a beam source for emitting a radiation beam to be supplied to the endoscope, and a beam source control unit for controlling the emission beam intensity of the beam source according to a beam quantity specified value input therein. The beam source control unit specifies the emission beam intensity corresponding to the beam quantity specified value based on at least three of control amounts. The control amounts include a control amount corresponding to pulse number modulation (PNM) control for changing lighting time of the beam source, a control amount corresponding to pulse width modulation (PWM) control for changing a plus width which indicates the lighting or lighting-out time within a control cycle, a control amount corresponding to pulse amplitude modulation (PAM) control for changing the lighting intensity, and a control amount corresponding to pulse density modulation (PDM) control for changing a lighting interval.
