A rear foot portion from the heel portion to the arch portion is attached to the rear foot attachment portion (130), and a forefoot portion from the arch portion to the toe portion is attached to the front foot attachment portion (140). Then, the rear leg attachment portion (130) and the front foot attachment portion (140) are formed such that when the foot portion is in the "heel separation" state at the time of walking or at the position of bottom flexion, the rotation axis So as to be substantially coincident with the position. When shifting to the "heel separation" state by taking a state of walking motion or bottom flexion position from the state where the entire sole is attached to the floor surface, with the first and second shaft members as the rotation axis, The rear foot mounting portion (130) and the front foot mounting portion (130) correspond to the movement of the sole extending when the rear flat plate member (131) in the mounting portion (130) Section mounting portion (140) increases. Therefore, smooth and stable movement of the foot portion can be realized when the articulation assist device is attached.踵部から土踏まず部にかけた後足部が後側足部装着部(130)に装着され、土踏まず部からつま先部にかけた前足部が前側足部装着部(140)に装着される。そして、後側足部装着部(130)及び前側足部装着部(140)は、歩行時や底屈位の体勢において足部が「踵離地」状態になるときの足部における回動軸位置と略一致するように、回動可能に取り付けられる。足裏全体を床面につけた状態から、歩行動作や底屈位の体勢をとることにより「踵離地」状態に移ると、第1及び第2軸部材を回動軸として、後側足部装着部(130)における後側平板部材(131)が回動し、「踵離地」状態になるときに足裏が伸びる動きに対応して、後側足部装着部(130)と前側足部装着部(140)との間隔が広がる。このため、関節運動アシスト装置を装着した場合において、スムーズかつ安定した足部の動きを実現することができる。
