It is difficult to develop a program for walking on two legs with a conventional motion assisting device capable of walking on two legs. An object holding unit 2 that holds an object 91； a body part 1 that supports a load from the object holding part 2； and a body part 1 that is rotatable about a body rotation axis parallel to a waist reference plane, Around the waist part 3 that supports the load from the upper body part 1, the wearer motion transmission part 17 that moves the waist part 3 according to the movement of the trunk of the wearer 90, and the opening / closing leg axis J5 that intersects the waist reference plane A thigh open / close leg 22 that is rotatably connected to the left and right of the waist, a thigh bone 25 that has one end connected to the thigh open / close leg 22, and a crus 5 that has one end connected to the other end of the thigh bone； The foot 6 that is connected to the other end of the lower leg and moves together with the wearer's foot, and the left and right ankle joints that the wearer 90 has landed by moving the waist 3 by the wearer motion transmitter 17 It is possible to control the position of the load center of gravity, which is the center of gravity of the load that is the total load applied to J9.従来の２足歩行ができる動作補助装置では、２足歩行させるプログラムを開発することが難しい。物体９１を保持する物体保持部２と、物体保持部２からの荷重を支える上体部１と、腰部基準面に平行な上体回転軸の回りに回転可能に上体部１に接続し、上体部１からの荷重を支える腰部３と、着用者９０の体幹の移動に応じて腰部３を移動させる着用者動作伝達部１７と、腰部基準面と交差する開閉脚軸Ｊ５の回りに回転可能に腰部の左右にそれぞれ接続する大腿開閉脚部２２と、大腿開閉脚部２２に一端が接続する大腿骨部２５と、大腿骨部の他端に一端が接続する下腿部５と、下腿部の他端に接続し、着用者の足とともに移動する足部６と、着用者９０が着用者動作伝達部１７により腰部３を移動させることで、着地している左右の足首関節部Ｊ９にかかる荷重の合計である負荷荷重の重心である負荷重心の位置を制御できる。
