An endoscope system comprises: an endoscope comprising an image pickup portion which performs image pickup； a signal processing apparatus which performs signal processing for an output signal from the image pickup portion； a signal transmitting portion which sends a video signal based on the output signal from the image pickup portion, by radio waves from the endoscope to the signal processing apparatus； and a transmission state detecting portion which detects a transmission state of the video signal in the signal transmitting portion. The signal transmitting portion includes: a signal sending portion and sends the video signal； and a signal receiving portion and receives the video signal sent by radio waves from the signal sending portion. The transmission state detecting portion detects the transmission state of the video signal by changing an output level of the signal sending portion or a receiving sensitivity level of the signal receiving portion.
