To provide a calibration device for an intake air oxygen concentration sensor, for calibrating output of an oxygen concentration sensor detecting intake air oxygen concentration to provide highly accurate output.

The calibration device for an intake air oxygen concentration sensor comprises: the oxygen concentration sensor 16 detecting concentration of oxygen in intake air; an intake passage pressure detection means 15; a calibration coefficient calculation means 37 calculating a calibration coefficient based on intake passage pressure and a reference output value of the oxygen concentration sensor 16; and a calibration means 37 calibrating the output of the oxygen concentration sensor based on the calibration coefficient. The calibration coefficient calculation means 37 stores the intake passage pressure when the calibration coefficient is updated, and updates the calibration coefficient only when the intake passage pressure detected by the intake passage pressure detection means is higher than the intake passage pressure stored the last time.