A movement assistance device includes: a back plate that is fitted onto the back of a wearer; a back frame that has an elongated shape and is supported by a rotating shaft fixed to the back plate so as to be rotatable in a plane parallel to the back plate; a side frame that is rotatably supported by a rotating shaft fixed to the back frame and parallel to the longitudinal direction of the back frame and extends from the back frame toward the vicinity of the side waist of the wearer; a thigh holding portion that is fitted onto the anterior thigh of the wearer; and a drive portion that is connected to each of the side frame and the thigh holding portion and generates force that increases the angle between the side frame and the thigh holding portion.