A gas supply source for supplying gas and a channel along which the gas is supplied can be easily switched by providing an instrument channel for passing an endoscope treating tool, a gas and water supply channel for supplying carbon dioxide etc. to the inside of a body, a gas supply source for a visceral cavity capable of supplying gas at a predetermined pressure, a gas supply source for a lumen capable of supplying gas at an optional pressure, and a switch device for switching from any of and an instrument channel and a gas and water supply channel to any of the gas supply source for a visceral cavity and the gas supply source for a lumen.
