a four - way reversing valve includes a valve casing having a plurality of ports through which fluid flows , a valve main body fixedly installed to the valve casing and having a valve chamber in which a plurality of main port connection holes for selectively connecting the ports are formed , a main spool rotatably installed at the valve chamber of the valve main body , for selectively connecting the ports according to a rotation position , and a spool driving unit for reversibly rotating the main spool by using part of fluid supplied through one of the ports in the valve casing . thus , the number of welding points is minimized by incorporating the overall pilot valves and excluding additional capillary connection for the pilot valves . also , manufacturing thereof is made easy and , during the manufacturing and use thereof , the rate of breakdown due to defective welding can be remarkably reduced .