An oil-immersed solenoid is provided with a casing including a base, a cylinder, and a flange in an integral manner, a fixed magnetic pole, a plunger having an armature, a guide pipe, a coil unit including a bobbin around which a coil is wound, and a cover, the fixed magnetic pole is integrated with the casing, and in the state where the plunger, the guide pipe, the coil unit, and the cover are attached in the cylinder of the casing, a front end of the cylinder is swaged, thereby holding the plunger, the guide pipe, the coil unit, and the cover in the casing.