To solve a problem wherein, although there are various types of temperature sensors for sensing an abnormal high temperature of various facilities and equipment irreversibly, a temperature sensor, which accurately operates, exhibits high durability and reliability, and is manufactured inexpensively, is difficult to find.

A liquid absorbing layer 4 formed of a liquid absorbent substance is arranged in a periphery of a center of a substrate 1 formed of insulating material so that an upper surface of the liquid absorbing layer is flush with an upper surface of the substrate 1. A pair of band-like electrode plates 6, 6 are oppositely arranged to be in contact with a pair of side edges 5 of the liquid absorbing layer 4. A hollow housing 7 is covered on an upper surface center of the substrate 1 to cover the electrode plates 6, 6. An insulating wax layer 8, which is formed of petroleum-based wax, has an insulation property and is dissolved at an optional set temperature, is formed on the upper surface of the substrate 1 in the hollow housing 7. Furthermore, a conductive wax layer 9, which is formed by kneading a conductive substance in a petroleum-based wax dissolved at a same temperature as the insulating wax layer 8, is superposed on an upper surface of the insulating wax layer 8 to structure the temperature sensitive switch for sensing an abnormal high temperature.