Sealed device for calibrating an altitude measurement device comprising an atmospheric pressure sensor whose movements of deformation are converted, via a transmission system, into a pivoting motion of an activation system that drives the pivoting of an indicator hand, wherein a sensing element bearing on the atmospheric pressure sensor is rigidly fixed to a transmission shaft movable along its longitudinal axis of symmetry, wherein the calibration device includes an air intake that can adjust the pressure inside the calibration device as required, and also includes a first button via which the axial position of the transmission shaft can be adjusted, and a second button via which it is possible to move the atmospheric pressure sensor up or down.The invention also concerns a method for calibrating the altitude measurement device using the sealed calibration device.