An reaction force adjustment member is attached to a suspension including a cylinder, a piston rod which has a piston at one end thereof and which is inserted into the cylinder together with the piston, and a diaphragm which has one end fixed to the cylinder and the other end fixed to the other end of the piston rod and which forms an air chamber around at least the piston rod. The reaction force adjustment member includes a cylindrical member which is provided on an outer circumference of the cylinder surrounded by the diaphragm when the suspension is extended and compressed. An outer circumference surface of the cylindrical member has an uneven surface.