A solenoid valve for a brake system enabling miniaturization of the valve and having an improved configuration to facilitate assembly and production of the valve. The solenoid valve includes an armature provided at one end thereof with an opening/closing member, a valve housing including a hollow first valve block fixed in a modulator block and a second valve block disposed below the first valve block and having an inlet for introduction of fluid, a valve seat installed in the first valve block and having a flow-hole to be opened or closed by the opening/closing member and a hollow extending longitudinally from the flow-hole, and an orifice sleeve located in the second valve block to define a fluid discharge passage and having an orifice formed in one end thereof to communicate with the hollow of the valve seat.