PURPOSE: To sense a prescribed temperature in a simple constitution and with high accuracy by adding a shape memory alloy member storing a shape to one or both of a pulse generation element and a permanent magnet in order to change the distance at a prescribed temperature between the pulse generation element and the permanent magnet that supplies the magnetic flux.

CONSTITUTION: The positive and negative magnetic fields are alternately applied to a pulse generation element 1 by means of a permanent magnet 2. The magnet 2 is attached to a shape memory alloy member 3 of a typical Ti-Ni alloy, etc., which stores a shape at a prescribed temperature to be sensed. Then the shape is stored so that the magnet 2 is kept away from the element 1 at a prescribed temperature. Under such conditions, the magnetic fields applied to the element 1 from the magnet 2 are decreased at a shape memory temperature and the pulse voltage of the element 1 is reduced or eliminated. As a result, the prescribed temperature can be sensed. The same effect is also secured if the element 1, instead of the magnet 2, is attached to the alloy member 3.