A switch comprising: a substrate, a lid body provided to overlap the substrate to form a switch case, a movable board rotatably arranged in the switch case; a plurality of fixed contact points provided on the substrate; movable contact points provided on the movable board, the fixed contact point and the movable contact point being connected/disconnected with rotation of the movable board; and a connecting piece portion extending inside the substrate to be connected to the fixed contact point, and being exposed as a terminal outside of the switch case, wherein the substrate and the lid body respectively include opposing surfaces opposing with each other in the peripheral edge of the switch case, a groove is provided in one of the opposing surface of the substrate and the opposing surface of the lid body, the groove being provided with a first welding interference portion formed in the depth portion, a projecting portion is provided in the other of the opposing surface of the substrate and the opposing surface of the lid body, the projecting portion being fitted in the groove and being provided with a second welding interference portion formed in a predetermined section in the overlapping direction, a ring groove for accommodating a seal ring is formed in the one of the opposing surface provided with the groove and the opposing surface provided with projecting portion, and the other is formed as a seal surface making contact with the seal ring, when the substrate and the lid body overlap, the switch case is sealed by contact between the seal ring and the seal surface and the substrate and the lid body are jointed by the welding between the first welding interference portion and the second welding interference portion, characterized in that: a release region for keeping a communicating state of an inside of the switch case with an outside is provided in any of the substrate and the lid body in a circumferential predetermined section, the release region keeps the communicating state until the seal ring makes contact with the seal surface in the jointing process between the substrate and the lid body, and wherein the release region is a notch cut-out of the second welding interference portion of the projecting portion. the substrate and the lid body respectively include opposing surfaces opposing with each other in the peripheral edge of the switch case, a groove is provided in one of the opposing surface of the substrate and the opposing surface of the lid body, the groove being provided with a first welding interference portion formed in the depth portion, a projecting portion is provided in the other of the opposing surface of the substrate and the opposing surface of the lid body, the projecting portion being fitted in the groove and being provided with a second welding interference portion formed in a predetermined section in the overlapping direction, a ring groove for accommodating a seal ring is formed in the one of the opposing surface provided with the groove and the opposing surface provided with projecting portion, and the other is formed as a seal surface making contact with the seal ring, when the substrate and the lid body overlap, the switch case is sealed by contact between the seal ring and the seal surface and the substrate and the lid body are jointed by the welding between the first welding interference portion and the second welding interference portion, characterized in that: a release region for keeping a communicating state of an inside of the switch case with an outside is provided in any of the substrate and the lid body in a circumferential predetermined section, the release region keeps the communicating state until the seal ring makes contact with the seal surface in the jointing process between the substrate and the lid body, and wherein the release region is a notch cut-out of the second welding interference portion of the projecting portion. a release region for keeping a communicating state of an inside of the switch case with an outside is provided in any of the substrate and the lid body in a circumferential predetermined section, the release region keeps the communicating state until the seal ring makes contact with the seal surface in the jointing process between the substrate and the lid body, and wherein the release region is a notch cut-out of the second welding interference portion of the projecting portion.