An object is to provide a light source device that can readily synchronize the lighting cycle of light sources and the rotation cycle of a light guide rod. Provided is a light source device (10) that includes LEDs (11) arranged in the form of a ring and each configured to emit illumination light; a light guide member (15) that optically guides the illumination light, emitted from each LED (11), along a central axis of the ring; a rotary motor that rotationally drives the light guide member (15) about the central axis; a reflective photo-sensor that detects rotation of the rotary motor; a CCD (5) that detects an amount of the illumination light optically guided by the light guide member (15); and a control section (6) that controls these sections and adjusts a phase difference between a lighting signal, which is used for performing lighting control of the LEDs (11), and a rotation detection signal, which is detected by the reflective photo-sensor, on the basis of the amount of light detected by the CCD (5).