Abstract: A xenon inhalation apparatus for introducing a mixed gas of xenon and oxygen into the lungs of a patient includes a respiration face mask, bellows having exhalation and inhalation ports, storing the mixed gas therein, and capable of varying its volume depending on the volume of the mixed gas stored therein, gas volume managing means, a series of conduit means for connecting the mask and the bellows, carbon dioxide removing means for removing carbon dioxide from exhalation gas in a closed loop system formed by the conduit means, gas flow rate control means, xenon concentration detecting means, xenon-supplying means, oxygen-supplying means, a controller for controlling the xenon-supplying means, oxygen-supplying means, electromagnetic valves and gas volume managing means, and an operation panel capable of at least setting the volume of the mixed gas stored in the bellows and the concentrations of xenon and oxygen to their respective optional values.