A method for calibrating a magnetometer. The magnetometer travels through (Si) a set of path positions, and acquires (S2) a plurality of measurements of the magnetic field. Trajectory information (S3) is provided representative of the location and the orientation of a point integral with the magnetometer. The measurements of the magnetic field are matched up (S4) with the trajectory information. A determination (S5) is made of calibration parameters of the magnetometer by the minimisation of a cost function involving, for a plurality of determination times, at least the calibration parameters, a measurement of the magnetic field, and a relationship linking the change in a magnetic field with the change in the location and in the orientation of the magnetometer derived from the trajectory information.