Switch apparatus

a The present invention aims at achieving the object of keeping a contact housing portion liquid tight sealed and to improve the durability of a switch apparatus. A switch apparatus according to the present embodiment includes: a switch case including a contact housing portion therein and a shaft hole ; a rod whose outer flange portion is capable of axially abutting on and engaging with a periphery portion of a detecting plate; a first return spring biasing the rod in the direction opposite to protruding direction; a fixed contact in the switch case and a movable contact which can reciprocally move between a position touching the fixed contact and a non-touching position; a diaphragm separating the shaft hole from the contact housing portion and being formed of rubber; a movable base supporting the movable contact and abutting on the diaphragm ; a second return spring bringing the movable contact into contact with the fixed contact ; and a retention member interposed between the diaphragm and the rod , including an abutting portion for abutting on the rod , and axially movably, but not rotatably supported with respect to the switch case