An oxygen concentration meter (10) includes a zirconia sensor (100), a resistor (110), a constant-current circuit (120), a resistance detection section (130), and an oxygen concentration detection section (150). The resistor (110) is connected in parallel to the zirconia sensor (100). The constant-current circuit (120) is connected in parallel to the zirconia sensor (100) and the resistor (110), and supplies an electric current. The resistance detection section (140) detects the resistance of the zirconia sensor (100) on the basis of the voltage of the zirconia sensor (100) in accordance with the supplied electric current. The oxygen concentration detection section (150) detects the oxygen concentration of gas to be measured that is supplied to the zirconia sensor (100), on the basis of the voltage of the zirconia sensor (100) resulting from an oxygen concentration difference between the gas to be measured and reference gas.