PURPOSE: To precisely and easily measure a heat history even when a place to measure is, for example, the internal part of a sealed system or driving system by mutually fusing and connecting a crystallized glass layer and an amorphous glass layer.

CONSTITUTION: This measuring element is formed of a first glass layer 11 consisting of crystallized glass and a second glass layer 12 consisting of amorphous glass. A reacting layer 13 is formed on the critical surface between the both when the glass layers 11, 12 are fused and connected together. Although this reacting layer 13 is grown by the heating to a prescribed temperature or more at temperature measurement, the reacting layer 13 is desirably thinned as much as possible so as to extend the measuring range and enhance the measuring precision. The reacting layer 13 is irreversibly grown by a fixed heating or more. According to it, the tension generated in the glass layer 12 is enhanced to cause a camber in the direction to which the tension is added. This camber has an uniform relation with the thickness of the reacting layer 13, and the heat history can be grasped by measuring the change of the camber quantity.