The gas-supply system includes a gas supply device that automatically supplies gas on the basis of the detection result of a pressure sensor that detects the pressure within a body cavity such that the pressure within the body cavity becomes a predetermined pressure, and a gas supply pipe for supplying the gas supplied from the gas supply device into the body cavity. The gas supply pipe is provided with a side face light leakage type optical fiber, and the gas supply pipe functions as a linear light emitter by controlling lighting of an LED according to the supply state of the gas due to the gas supply device and makes the light from the LED incident on the side face light leakage type optical fiber. Therefore, the supply state of the gas supplied into the body cavity may be easily grasped.
