A spool valve is provided which improves the responsiveness of the object to be hydraulically controlled, such as a V-belt type continuously variable transmission, and which improves the overall safety. The spool valve includes a spool (40) inserted in a spool insertion hole (32) formed in a valve body (31), The spool is moved by an electric motor (12) via a ball-screw (21) to a first position where the input port (37) communicates with the output port (38), while the output port (38) is not in communication with the drain port (39), and to a second position where the input port (37) is not in communication with the output port (38), while the output port (38) communicates with the drain port (39).