This endoscope system includes: a distal end portion which is inserted inside a specimen and which has an imaging section that creates video signals, a video signal processing section that processes the video signals, a video transmitting section that transmits the processed video signals, a timing signal creation section that creates a timing signal needed to drive the imaging section, the video signal processing section, or the video transmitting section, and a base clock receiving section that receives as an optical signal a base clock which is the basis of the timing signal and then converts the received optical signal into an electrical signal and an external apparatus having an insertion portion which guides the distal end portion into the specimen, a monitor that displays the video signals, and a video processor that processes the video signals from the distal end portion and outputs them to the monitor.
