Disclosed is an operating position changeable loading apparatus with multi-axis joint movement used on machining center. The apparatus consists of a load-receiving test piece and a load-exerting component. Moving the load-exerting component and the load-receiving test piece to a preset loading position according to a multi-axis joint movement, with the displacement value measured by displacement sensors and the amount of simulated load measured by a force sensor of the loaded-exerting component, a stiffness of the load-exertion position under a simulated load can be derived. Changing the load-exertion position, repeating in sequence the previous steps, a stiffness distribution under the simulated load can be derived.