The concave streak portion 26, in which the welding inclination surface 27 is formed, is provided on the side wall 12; the projecting portion 40, which is fitted into the concave streak portion 26 when the substrate 10 and the lid body 35 overlap to form the switch case 3, is provided on the lid body 35; when the substrate 10 and the lid body 35 are overlapped, the switch case 3 is sealed by contacting the seal ring 31 with the flange portion 38 and the welding shoulder portion 41 interferes with the welding inclination surface 27; the substrate 10 and the lid body 35 are jointed by melting the interference portion by high-frequency welding; the release region K, which keep the communicating state of the inside of the switch case 3 with the outside is designed by notching the projecting portion 40 from the root thereof.