PURPOSE: To detect the oxygen concentration quickly and simply by a method wherein gas without oxygen is introduced into a cell from the gas introduction tube of a device comprising an oxygen detection element, the output thereof, an amplifier, a recorder and the like and then, a matter to be inspected is injected thereinto from a lid after the halting of the introduction thereof.

CONSTITUTION: The detector of oxygen concentration comprises an oxygen detection element 1, the output thereof, an amplifier 6, a recorder 7 and the like. A gas without oxygen is introduced into a cell 11 from a gas introduction tube 3 of the detector is introduced and a matter to be inspected is injected thereinto from a lid 5 after the halting of the introduction thereof. At the same time, the power source of a magnetic stirer 9 is turned on to detect a partial pressure of oxygen in the cell 11 with an oxygen detection element 1 rotating a stirer 10 and changes in the rise of the output thereof is recorded. In this case, the increase in the output is proportional to the oxygen concentration of the matter being inspected. According to this method, electrochemical measurement of the oxygen concentration can be done quickly and accurately with an extremely simple apparatus even the concentration is extremely low.