PURPOSE: To establish the liquid temperature sensing detector with a simple construction which can detect average water temperature excellently, by wrapping the thermal conductor with thermo strage insulator and fitting the heat sensing element at the upper end of the thermal conductor.

CONSTITUTION: The thermal conductor 2 such as copper is enclosed with the heat storage insulator 1 such as plastic and glass, the heat sensing element (chip thermister) 3 is directly bonded to the upper end of the thermal conductor 2 at the electrode 8 of one side, and the lead 12 is connected to another side of the electrode 13 and the lead 11 is to the terminal 10 of the thermal conductor 2. Further, at the external circumference of the heat storage insulator 1, the first electrode 4 and second and third electrodes 5 and 6 connecting the leads 14, 15, 16 respectively are fitted, and the said leads are bundled in the tube 17 and led out through the water proof rubber cap 18. By using the said detector, when the water level is between the first electrode 4 and the second(3) electrode 5(6), the output current of the element 3 is detected and the average temperature of liquid can be measured by multiplying a given coefficient to it.