A light source apparatus for an endoscope includes an exciting laser light source, a monitor sensor, an indicator, a shutter mechanism, an optical system, and a controller. The controller intermittently turns on the exciting laser light source for testing and controls the shutter mechanism so as to close the optical path of the exciting light, during a period after laser irradiation is permitted until the monitor sensor outputs the turn-on enable signal. The controller controls the shutter mechanism so as to open the optical path of the exciting light and controls the indicator so as to indicate to the effect that the exciting laser light source is ready for immediate emission, when the monitor sensor outputs the turn-on enable signal. Further, the controller turns on the exciting laser light source when an exciting light turn-on signal is input, thereby making the exciting light incident upon the light guide.