We propose a wrist joint motion measuring device that can be applied to training devices. In this study, we developed a wrist motion measurement method that uses wearable parallel-link mechanisms to continuously measure the hand in exercise. The proposed method is non-invasive and has a simple mechanism that uses compact linear encoders. The equipment is attached to the human hand and lower arm via a glove and belts. In experiments, the radial flexion and ulnar flexion motions of 12 subjects were measured, and the obtained results were compared with previous anatomical results. The validity of the proposed method was demonstrated.