To structure a thermal valve W capable of speeding up opening and closing actuation of a valve mechanism 1 while maintaining characteristics of the thermal valve W which does not generate a water hammer phenomenon whithout generating a defect.

The thermal valve W is structured of a temperature sensing part 23 formed in a case shape of a metal material and housing a thermally actuated element 22, a guide tube part 25 which is connected to a base end side of the temperature sensing part 23 by caulking and which an actuation shaft 24 is engaged and inserted in a bore, a heating element 20 formed in a disc shape and abutted on the temperature sensing part 23 by sandwiching by electrode plates 21, 21, and the valve mechanism 1 actuated to open and close by the actuation shaft 24. A diameter of a part of a tip end side from an end surface 23b on a tip end side to a front of a caulking part 23a for caulking the guide tube part 25 of the metal material for forming the temperature sensing part 23 is reduced from an outer circumference side so as to reduce an area ratio and a diameter ratio to the heating element 20, and a mass of the temperature sensing part 23 is reduced. Thereby, a time from when energization becomes on to when the valve mechanism 1 is actuated is contracted.