An apparatus includes a first wire and a second wire which are coupled to a right upper ankle belt and a right lower ankle belt, a third wire and a fourth wire which are coupled to a left upper ankle belt and a left lower ankle belt, an obtainer obtaining information about a road surface where a user walks, and a controller controlling tensions of the first wire and the second wire at the same time and controlling tensions of the third wire and the fourth wire at the same time using a first stiffness target value corresponding to the first wire, a second stiffness target value corresponding to the second wire, a third stiffness target value corresponding to the third wire, and a fourth stiffness target value corresponding to the fourth wire that are determined based on the information about the road surface.