To measure dynamic and mechanical impedance of an articulated musculoskeletal system during exercise by successively inducing by imparting an induction external force on the articulated musculoskeletal system and successively estimating the mechanical impedance dependent on the state of the muscle.

An induction external force is acted on the musculoskeletal system 0 by an induction external force means 1 for applying an induction external force to the musculoskeletal system, the induction point of the musculoskeletal system 0 is measured by an induction point measuring means 2, and the induction external force applying on the musculoskeletal system 0 is measured by the induction external force measuring means 3. An induction change extraction module 4 extracts only the position and the component changed by induction of the muscle generation force from the measured induction position and induction external force by using the dynamic model of the arm and a coefficient successive estimation module 5 successively calculates the mechanical impedance of the musculoskeletal system 0. The calculation necessary for the modules 4, 5 are realized by, for example, a computer 6.