PURPOSE: To obtain an I-shaped plunger solenoid having a movable iron core with a high return stability thereby to make it possible to raise the response reliability of an electromagnetic valve, by forming subdividing grooves in a magnetically attracting surface of either one of the movable iron core and a fixed iron core.

CONSTITUTION: A movable iron core 1 has a vertical groove 3 for exhaust, a cylinder 8 resiliently pressed by a compression coiled spring 5 and receiving a hard rubber exhaust valve 7, and a spider's web-shaped magnetically attracting surface subdividing groove 63, formed on a magnetically attracting surface 6, constituting divided magnetically attracting surfaces 62 each having a small area by ripple-shaped annular grooves 60 and radial grooves 61. While being in a magnetically attracting relation to a magnetically attracting surface of a fixed iron core, the attracting surface 6 is in a pressurized state since air flows into the annular grooves 60 and the radial grooves 61 of the subdividing groove 63 from the cylinder 8 and the vertical groove 3. Therefore, the synergistic effect of the magnetically attracting relationship therebetween and the pressurized state overcomes the fluid pressure resulting from generation of a seal region, thereby allowing a high return stability of the movable iron core when an electromagnetic coil is deenergized to close the valve. Accordingly, it is possible to largely improve the response reliability in the valve function.