The present invention aims to provide an air-micrometer calibration device capable of securely causing an axis of a measuring-head tip portion and an axis of a master hole to coincide with each other. To this end, the air-micrometer calibration device (91) includes a small-diameter master hole (95); a large-diameter master hole (96); and positioning means for causing an axis of the measuring-head tip portion and an axis of the small-diameter master hole to coincide with each other when a measuring-head tip portion (43) is inserted in the small-diameter master hole (95), and for causing the axis of the measuring-head tip portion and an axis of the large-diameter master hole to coincide with each other when the measuring-head tip portion is inserted in the large-diameter master hole, where the positioning means includes: a pressure oil supply passage (98); a clamping sleeve (93); and a hydraulic pressure chamber (97) surrounding a periphery of the clamping sleeve, and the clamping sleeve clamps a measuring-head body portion (42) (a case (46)) in association with a pressure of a pressure oil supplied from the pressure oil supply passage to the hydraulic pressure chamber.