To obtain high reliability against leakage of a working fluid with reduced manufacturing cost.

A valve housing 3 is equipped with: a metallic base metal A; and an outer circumferential shape forming resin B for forming the outer peripheral shape, while the outer peripheral shape forming resin B is equipped with an O-ring resin inner wall B1 at a side of a back of an outer O-ring groove 43. The O-ring resin inner wall B1 is not arranged at the bottom of the outer O-ring groove 43 to thereby expose the base metal A at the bottom of the outer O-ring groove 43. Thus, because of providing a complicated surficial shape by means of the outer peripheral shape forming resin B, the cost is reduced. Because of interposing no resin member between the base metal A and an outer O-ring 33, there occurs no gap caused by a crack of the resin member between the base metal A and the outer O ring 33. As a result, the high reliability against the leakage of the working fluid is provided, while the manufacturing cost of a three-way electromagnetic valve is reduced.