An assistance device according to one embodiment assists with leg joint movement, and comprises a drive unit, an elastic unit, and a crank mechanism. The drive unit comprises a motor and a transmission mechanism for changing the speed of the motor, and converts rotational movement of the motor into linear movement. The elastic unit comprises: at least a series spring provided in series between the transmission mechanism and the crank mechanism； a first parallel spring provided between the drive unit and an ankle section； and a second parallel spring provided between the ankle section and a foot section. The elastic unit: reduces, using compression, an impact from an object, which is transmitted via the foot section； accumulates impact force or user gravitational force； and releases the accumulated energy by extension to impart a bias for assisting with movement. The crank mechanism is provided between the drive unit and the foot section, converts the linear movement to rotational movement and transmits the rotational movement to the foot section while changing the deceleration factor in accordance with an ankle angle.一個實施方式的輔助裝置輔助下肢關節動作，具備驅動部、彈性部以及曲柄機構。所述驅動部包括電動機和改變該電動機速度的變速機構，將所述電動機的旋轉運動變換為直線運動。所述彈性部至少包括：串聯彈簧，其串聯設置在變速機構與曲柄機構之間；第1並列彈簧，其設置在驅動部與腳關節部之間；以及第2並列彈簧，其設置在腳關節部與腳部之間，通過壓縮來緩和經由腳部來自對象物的衝擊，並且蓄積該衝擊力或自重力，通過伸長釋放蓄積的能量來給與用於動作輔助的施力。所述曲柄機構設置在所述驅動部與腳部之間，一邊根據腳關節角度來改變減速係數，一邊將所述直線運動變換成旋轉運動來傳遞給腳部。
