This invention provides a sensor or its related art to be easily used for measuring motor function of living body. This invention relates to a sensor for measuring motor function, which includes a magnetic field generator attached to one of two predetermined positions in a living body changing mutual distance caused by an action of the living body to have a coil board generating a magnetic field by electrification, and a magnetic field detector attached to the other of the two predetermined positions in the living body to detect the magnetic field generated by the magnetic field generator and have the coil board generating an electric current having a magnitude corresponding to a strength of the magnetic field as detected. Furthermore, each of the magnetic field generator and the magnetic field detector is provided with plastics covering a whole coil board thereof.