A solenoid valve includes a main poppet configured to control a flow rate of working fluid flowing in a valve passage according to a pilot pressure, an auxiliary poppet configured to adjust the pilot pressure according to the electromagnetic force, and a first seat portion and a second seat portion provided in the valve passage. The main poppet includes a poppet valve seated on the first seat portion and a spool valve slidable in the second seat portion. The spool valve includes an outer peripheral surface slidable relative to the second seat portion and through holes open on the outer surface and configured such that areas thereof exposed from the second seat portion change in accordance with a movement of the spool valve.