PROBLEM TO BE SOLVED: To appropriately absorb a difference in body size of a wearer, suppress a decrease in transmission efficiency of an assist force, have good followability to the movement of the wearer, and do not generate an assist force during a walking motion. However, it provides an assist device that allows the wearer to walk comfortably. SOLUTION: A waist mounting band 5, a shoulder mounting band 3, an actuator 25, a power transmission member 21C connected to the actuator, and a pulley to support a leg side pulley 32C by transmitting a force from the power transmission member. The support portion 31ZC, the leg side pulley which is a pulley arranged below the pulley support portion, the two knee connecting members 22C which are hung on the leg side pulley and both ends are connected to the waist mounting band, and both knee connecting members. The left leg pulley 33CL and the right leg pulley 33CR hung, the left knee mounting band 9L and the right knee mounting band 9R connected to the left leg pulley and the right leg pulley, the posture detecting device for detecting the posture of the wearer, and the posture detecting device. It has a control device 52 that controls an actuator based on the posture information of the wearer. [Selection diagram] FIG. 12【課題】軽量であり、装着者の体格差を適切に吸収してアシスト力の伝達効率の低下を抑制し、装着者の動作への追従性がよく、歩行動作時はアシスト力を発生させなくても装着者が楽に歩行することができるアシスト装置を提供する。【解決手段】腰部装着帯5と、肩部装着帯3と、アクチュエータ25と、アクチュエータに接続された動力伝達部材21Cと、動力伝達部材からの力が伝達されて脚側プーリ32Cを支持するプーリ支持部31ZCと、プーリ支持部の下方に配置された滑車である脚側プーリと、脚側プーリに掛けられて両端が腰部装着帯に接続された両ひざ連結部材22Cと、両ひざ連結部材に掛けられた左脚プーリ33CL及び右脚プーリ33CRと、左脚プーリ及び右脚プーリに接続される左ひざ装着帯9L及び右ひざ装着帯9Rと、装着者の姿勢を検出する姿勢検出装置と、装着者の姿勢情報に基づいてアクチュエータを制御する制御装置52と、を有する。【選択図】図12