To provide a safety switch which can prevent over-charging by switching off a battery due to a thermal shrinkage tube getting shrunken at a time of occurrence of over-heating because of an irregular driving of the battery and by shutting down an external current for charging a battery cell and which consumes internal energy by a resistance member and can secure battery safety.

The safety switch is provided with a tube with a shrinking property at more than a predetermined temperature (a thermal shrinkage tube). The thermal shrinkage tube can perform variation for controlling conduction of a current and when one part of the thermal shrinkage tube is fixed, the other part is connected with a cable connection part so that conductive connection or disconnection is triggered by a variation of a length due to heating.