An electromagnetic device comprising: - a fixed iron core; - a movable iron core which is disposed to face the fixed iron core with a drive shaft fixed to a central portion and is displaceable in an axis line direction of the drive shaft between a retreated position away from the fixed iron core and an advanced position coming close to the fixed iron core; - an electromagnetic coil provided in the fixed iron core; - a permanent magnet which retains the movable iron core at the advanced position; - a plurality of supporting posts which are provided parallel to the axis line direction on both side surfaces of the fixed iron core and support the fixed iron core; - an opening-side plate which is provided at one end portion of the supporting post on the movable iron core side in a longitudinal direction and in which the drive shaft passes therethrough and is supported; and - a closing-side plate which is provided at the other end portion of the supporting post in the longitudinal direction and in which the drive shaft passes therethrough and is supported, wherein the advanced position of the movable iron core is restricted by the fixed iron core, and the retreated position is restricted by the opening-side plate, characterized in that: each of the opening-side plate and the closing-side plate has a bearing mounting hole in which a bearing for the drive shaft passing therethrough is mounted, and supporting post mounting holes (14b,14c), in each of which the supporting post is mounted, wherein the fixed iron core is configured by laminating thin plates, and wherein the supporting post mounting hole for the supporting post which is mounted on a surface on one side of the fixed iron core in a lamination layer direction, among the plurality of supporting posts supporting the fixed iron core, is formed to be positioned in a predetermined dimension on the basis of the bearing mounting hole, and the supporting post mounting hole for the supporting post which is mounted on a surface on the other side is formed to have a size in which the supporting post can be mounted even if a mounting position is varied within a dimensional tolerance of a thickness in the lamination layer direction of the fixed iron core. - a fixed iron core; - a movable iron core which is disposed to face the fixed iron core with a drive shaft fixed to a central portion and is displaceable in an axis line direction of the drive shaft between a retreated position away from the fixed iron core and an advanced position coming close to the fixed iron core; - an electromagnetic coil provided in the fixed iron core; - a permanent magnet which retains the movable iron core at the advanced position; - a plurality of supporting posts which are provided parallel to the axis line direction on both side surfaces of the fixed iron core and support the fixed iron core; - an opening-side plate which is provided at one end portion of the supporting post on the movable iron core side in a longitudinal direction and in which the drive shaft passes therethrough and is supported; and - a closing-side plate which is provided at the other end portion of the supporting post in the longitudinal direction and in which the drive shaft passes therethrough and is supported, each of the opening-side plate and the closing-side plate has a bearing mounting hole in which a bearing for the drive shaft passing therethrough is mounted, and supporting post mounting holes (14b,14c), in each of which the supporting post is mounted, wherein the fixed iron core is configured by laminating thin plates, and wherein the supporting post mounting hole for the supporting post which is mounted on a surface on one side of the fixed iron core in a lamination layer direction, among the plurality of supporting posts supporting the fixed iron core, is formed to be positioned in a predetermined dimension on the basis of the bearing mounting hole, and the supporting post mounting hole for the supporting post which is mounted on a surface on the other side is formed to have a size in which the supporting post can be mounted even if a mounting position is varied within a dimensional tolerance of a thickness in the lamination layer direction of the fixed iron core.