Abstract: A breathing apparatus includes: a vessel member having a mouth piece and internal influx chamber; a tubular communication member having opposite ends connected respectively to the intake and outgo ports of the vessel member in such a manner that the vessel member and the communication member define a circular passage for a respirable gas; an oxygen-supplying mechanism for supplying the circular passage with the respirable gas; a pair of check valves, disposed respectively at the intake and outgo ports of the vessel member, for limiting the flow of the respirable gas in the circular passage to a single direction so that, when the person breathes into the influx chamber, the respirable gas in the influx chamber is introduced into the communication member through the outgo port and, when the person inhales through the mouth piece, the respirable gas in the communication member is recycled into the influx chamber through the intake port; and an outlet port for discharging excess respirable gas out of the circular