To provide a joint motion analyzing apparatus providing precise joint motion information over time using a three-dimensional CT (computed tomography) image.

The joint motion analyzing apparatus extracts a bone ROI (Region Of Interest) relative to a plurality of CT images obtained by capturing a same subject over time using X-ray CT equipment based on a predetermined threshold, sets local coordinates for every extracted bone ROI, calculates relative variations (amount of displacement, speed, acceleration, angle, angular velocity, and angular acceleration) of a plurality of bone ROIs caused by the joint motion (bending, stretching, adduction, abduction, inner rotation, external rotation, or the like) based on each of local coordinates for every bone ROI, and quantifies the joint motion constituting the bone ROI as the motion information.