An expansion valve comprising: a valve main body having a first passage (110, 142) in which a high-pressure refrigerant passes from a condenser to an evaporator, an orifice provided at the middle of the first passage (110, 142) and for reducing pressure of the high-pressure refrigerant, and a second passage in which a low-pressure refrigerant passes from the evaporator to the condenser; a valve body for opening/closing the orifice; and a power element for driving the valve body based on a temperature and pressure on the outlet side of the evaporator, wherein the valve main body is formed by an extrusion molding, wherein the valve main body has a hexahedral prismatic shape, the valve main body comprises two opposing first side faces (100a, 100b) being adapted to be held by a chuck mechanism, two opposing second side faces (100c, 100d), and upper and lower faces (100e, 100f), wherein the two opposing second side faces (100c, 100d) and the upper and lower faces (100e, 100f) are adapted to be machined to form the first passage (110, 142), the second passage, the orifice and an attaching hole of the power element, characterized in that each of the first side faces (100a, 100b) has a pair of flat holding faces (101a, 101b, 102a, 102b), wherein the flat holding surfaces (101a, 101b, 102a, 102b) are in parallel to each other and are adapted to be held by the chuck mechanism, wherein portions other than the flat holding faces (101a, 101b, 102a, 102b) of the first side faces (100a, 100b) are formed to have concave parts which are concave more on the inner side than the flat holding faces (101a, 101b, 102a, 102b), and wherein the flat holding faces (101a, 101b, 102a, 102b) are formed as outermost faces among faces of the first side faces (100a, 100b) at a time of an extrusion molding. a valve main body having a first passage (110, 142) in which a high-pressure refrigerant passes from a condenser to an evaporator, an orifice provided at the middle of the first passage (110, 142) and for reducing pressure of the high-pressure refrigerant, and a second passage in which a low-pressure refrigerant passes from the evaporator to the condenser; a valve body for opening/closing the orifice; and a power element for driving the valve body based on a temperature and pressure on the outlet side of the evaporator, wherein the valve main body is formed by an extrusion molding, wherein the valve main body has a hexahedral prismatic shape, the valve main body comprises two opposing first side faces (100a, 100b) being adapted to be held by a chuck mechanism, two opposing second side faces (100c, 100d), and upper and lower faces (100e, 100f), wherein the two opposing second side faces (100c, 100d) and the upper and lower faces (100e, 100f) are adapted to be machined to form the first passage (110, 142), the second passage, the orifice and an attaching hole of the power element, characterized in that each of the first side faces (100a, 100b) has a pair of flat holding faces (101a, 101b, 102a, 102b), wherein the flat holding surfaces (101a, 101b, 102a, 102b) are in parallel to each other and are adapted to be held by the chuck mechanism, wherein portions other than the flat holding faces (101a, 101b, 102a, 102b) of the first side faces (100a, 100b) are formed to have concave parts which are concave more on the inner side than the flat holding faces (101a, 101b, 102a, 102b), and wherein the flat holding faces (101a, 101b, 102a, 102b) are formed as outermost faces among faces of the first side faces (100a, 100b) at a time of an extrusion molding.