An oxygen concentrator for supplying high concentration oxygen stably to a patientregardless of the environmental temperature and/or the flow rate of high concentrationoxygen gas. The oxygen concentrator comprises an oxygen concentration sensorfor detecting the concentration of oxygen gas produced from the oxygen concentrator,a temperature sensor for measuring the environmental temperature and/or a flowsensor. The oxygen concentrator performs control for maintaining the concentrationof oxygen at a predetermined level by increasing/decreasing the quantity ofair supplied by a pressurized air supply means based on the detection value ofoxygen concentration, and changes a control means by the measurements of thetemperature sensor and/or the flow sensor of the oxygen concentrator.
