An imaging element (23) performs imaging at a frame rate higher than a frame rate of display of a captured image displayed by a display device (7). A light source device (5) repeatedly performs an operation of continuously emitting illumination light in a first period over a plurality of consecutive frames in imaging by the imaging element (23), and then emitting illumination light having a spectrum different from a spectrum of the illumination light emitted in the first period in a second period which is a period over at least one frame in imaging by the imaging element (23).