The purpose of the invention is to provide a low-pressure chamber with tsunami shelter function that can withstand extreme earthquake movement, withstand extreme mud flows even if a large tsunami should strike, withstand strong impact from debris, drift for a long while waiting for rescue, and be used as a low-pressure chamber for promoting health during normal times. An enclosure comprises an air supply nozzle, a ventilation nozzle, and an enclosure window on a side face. An emergency shutoff valve, a check valve, and a ventilation means for venting the air inside the enclosure are each connected in series, in order from the enclosure side, to the ventilation nozzle with piping. An emergency shutoff valve, a main air filter, a preliminary air filter, and a pressure control valve are each connected in series, in order from the enclosure side, to the air supply nozzle with piping. The pressure inside the enclosure can be controlled to a desired pressure curve by opening and closing the pressure control valve while continuously venting air inside the enclosure by starting the ventilation means. An airtight door comprises a door window. A window glass protection means that can protect the window glass is provided on the window glass provided in the enclosure window and on the window glass provided in the door window.