To provide a switch device capable of dealing with various specifications of a vehicle-side connector of a fitting mate while having high waterproof performance and kept from being easily broken.

A switch part is formed in an internal space surrounded by a body 1 and a terminal base 2 fixed inside the body 1 so as to expose a part thereof from one end face of the body 1, connection terminals 10a and 10b for transmitting a switching signal of the switch part to the outside are so installed as to project from one end of the terminal base 2, a connector housing 13 is so mounted and fixed to the terminal base 2 as to cover the connection terminals 10a and 10b, and thereafter a waterproof cover 14 is so formed by outsert molding as to cover the outside surface of the device from the one end face of the body 1 through the connector housing 13.