An endoscope system includes an endoscope including a CCD for generating an image pickup signal, and a processor including a video processing circuit. The processor includes: a VCXO that generates a reference clock signal； a PLL circuit that synchronizes a phase of the image pickup signal to be inputted and a phase of the reference clock signal； a synchronization detection circuit that detects whether the phase of the image pickup signal synchronizes with the phase of the reference clock signal； and a multiplexer that controls the video processing circuit, on the basis of the detection result by the synchronization detection circuit, to cause the video processing circuit to output a predetermined video when a non-phase-synchronized state is detected, and to cause the video processing circuit to output a video signal obtained by processing the image pickup signal by the video processing circuit when a phase-synchronized state is detected.
