To provide a tool for assembling valve components, capable of avoiding concerns on assembly with a simple structure and operation.

The tool 11 includes: a rod-like tool body 11a that has a small diameter than an inside diameter of a spool hole 4d, an outside diameter larger than an inside diameter of a regular spring 9 and has a seating surface 11c abutting on an end surface 9a of a spring 9; a pressure portion 11b that is formed to extend to the opposite side of the seating surface 11c and applies pressing force to the tool body 11a; a key groove 11d communicatable with a key hole 4e is formed on the seating surface 11c of the tool body 11a; and a relief hole 11e having a larger diameter than an outside diameter of an irregular spring 19 that has a smaller diameter than the regular spring 9.