Abstract: A method for calibrating an inertial measurement sensor in an accurate manner even when the sensor is attached to a patient who has difficulty in standing upright or maintaining an upright posture due to a posture or movement impairment. The method includes attaching an inertial measurement sensor (2) for detecting three-axis acceleration and three-axis angular velocity to each of a torso, a femoral part and a crural part of a user (U) for measuring a movement of the user, and having the user sit on a chair (20) in a standard posture in which the torso and the crural part of the user are substantially parallel to each other, and the femoral part is substantially orthogonal to the torso and the crural part, and calibrating the inertial measurement sensors by using outputs of the inertial measurement sensors when the user is in the standard posture as reference values.