When observation or treatment in a lumen is performed by an endoscope, pressure in the lumen is measured precisely and air supply is performed so as to keep the pressure appropriate.An endoscope air-supply system is provided which includes a gas supply device which supplies predetermined gas to a lumen of a subject through an air-supply duct； a pressure measurement device which measures pressure in the lumen and which is connected through a duct for pressure measurement communicating with the lumen； a flushing device which supplies gas for flushing to the duct for pressure measurement； and an instruction device which instructs the pressure measurement device to perform pressure measurement and which instructs the flushing device to supply the gas for flushing in synchronism with the pressure measurement by the pressure measurement device.
