An endoscope system 1, including: an endoscope 2 for picking up an image of a subject 10 and outputting an image pickup signal of the image； an external processor 3 having a post-signal processing circuit 30 which processes the image pickup signal inputted from the endoscope 2 and generates a video signal that can be outputted to a monitor 4； and an output detecting circuit 31 for detecting the presence or absence of an output of the image pickup signal and the presence or absence of an output of the video signal.
