Disclosed is a solenoid valve for a brake system, the solenoid valve including a magnet core that is provided in a cylindrical shape, is installed in a bore of a modulator block, and has a through-hole opening in a lengthwise direction thereof and a radial direction passage communicating with the through-hole; an armature that is installed at one end of the magnet core so as to be reciprocated; a valve seat that is provided at the other end of the magnet core and has an orifice; a plunger that is inserted into the through-hole and performs a sliding motion by the armature to open and close the orifice; a sleeve that is fixed to the bore while accommodating the armature and the magnet core; and a return spring that is provided to apply an elastic restorative force to the plunger to open the orifice, wherein a passage hole is provided in a spiral shape along the through-hole at an inner circumferential surface of the magnet core to discharge air between the magnet core and the plunger and air between the magnet core and the armature.