The muscle force assisting device is relatively rotatable with respect to the first wearing tool about the assist axis, the first wearing tool being attached to one of the two parts of the human body between which the joint is located. A second mounting tool attached to the other of the first mounting tool, and a rotating member that is rotatably supported around the assist axis with respect to the first mounting tool and connected to the second mounting tool. The second mounting tool is a mounting part that is attached to the other of the two parts of the human body, a connecting arm part that extends from the rotating member in a direction non-parallel to the assist axis and connects the rotating member and the mounting part, Have The connecting arm portion and the mounting portion are connected so as to be relatively rotatable.筋力補助装置は、関節が間に位置する人体の二つの部位のうちの一方に取り付けられる第１装着具と、アシスト軸線を中心として第１装着具に対して相対回転可能であり、二つの部位のうちの他方に取り付けられる第２装着具と、第１装着具に対してアシスト軸線を中心として回転可能に支持され且つ第２装着具に接続した回転部材と、を有する。第２装着具は、人体の二つの部位のうちの他方に取り付けられる装着部と、回転部材からアシスト軸線と非平行な方向に延び出して回転部材と装着部とを連結する連結アーム部と、を有する。連結アーム部と装着部は相対回転可能に接続している。
