Abstract: A joint motion measuring apparatus is applied for measuring a rotation angle of a joint. A human body has a moving part connected with the joint. The joint motion measuring apparatus includes an attitude sensing unit, an attitude computing unit, and a joint motion computing unit. The attitude sensing unit is placed on the moving part, and senses the moving part moving from a first position to a second position to output a motion sensing signal. The attitude computing unit is coupled with the attitude sensing unit and transfers the motion sensing signal into an attitude signal. The joint motion computing unit is coupled with the attitude computing unit, and computes a zenith angle of the attitude sensing unit at the second position according to the attitude signal to further obtain the rotation angle of the joint according to the zenith angle.