To provide a solenoid valve which does not cause unexpected leakage of operation liquid when it is not operated.

In this solenoid valve, a sleeve 26 is movably inserted into a spool. The sleeve 26 is moved by a movable core 48 of a proportional solenoid mechanism 6 through an engagement member 51. A stepped spool 10 influences nothing of certain movement of the movable core 48. An outer diameter of the stepped spool 10 can be reduced to required minimin size, so that a sectional area between the stepped spool 10 and the sleeve 26 is reduced for suppressing leakage of operation liquid. The sleeve 26 is inserted into the stepped spool 10 in a movable manner, while the stepped spool 10 is moved by the proportional solenoid mechanism 6 through the engagement member 51, so that the size of the proportional solenoid mechanism 6 is not influenced by the diameter of the stepped spool 10. In addition, increase of size of the proportional solenoid mechanism 6 can be avoided even when the diameter of the stepped spool 10 is increased.