A switch device capable of safely opening or short-circuiting an electrical circuit in response to an abnormality such as wetting with water or liquid leaking from a battery is provided. The device includes a conductor connected to an external circuit, and a reaction part including a liquid-soluble material which opens the conductor and the external circuit and which dissolves on contacting a liquid entering the device interior to electrically connect the conductor and the external circuit.

A switch device capable of safely opening or short-circuiting an electrical circuit in response to an abnormality such as wetting with water or liquid leaking from a battery is provided. The device includes a conductor connected to an external circuit, and a reaction part including a liquid-soluble material which opens the conductor and the external circuit and which dissolves on contacting a liquid entering the device interior to electrically connect the conductor and the external circuit.