An expansion valve for reducing the quantity of material required for the valve body by contriving the arrangement of bolt fitting grooves. In the expansion valve (20), displacement of a valve member driver (36) provided in the valve body (21) is transmitted to a valve member by a valve member drive rod (36f) and the valve opening is altered to control the flow rate of the refrigerant. The valve body (21) consists of a body upper portion (40) and a body lower portion (41) narrower than the body upper portion (40), and bolt fitting grooves (43, 43) opening in the flank of the valve body (21), preferably opening obliquely downward, are formed at the boundary (42) of the body upper portion (40) and the body lower portion (41). With such a layout, the material required at the boundary (42) can be reduced furthermore and the quantity of material required for the valve body (21) can be reduced furthermore, as a result. Since the opening width (minimum spatial dimension) w is smaller than the diameter of bolt, a seating surface is assured sufficiently around the bolt fitting groove (43) and the bolt does not drop off from the bolt fitting groove (43).