First and second multi-pair thermocouples (21, 22) are formed on the upper surface of a heat-sensitive member (10), and a thermally uniformizing member (30) is adhesively attached to a base portion (11) of the heat-sensitive member (10). The thermally uniformizing member (30) is formed of a heat-resistant and electrically insulating material having a higher thermal conductivity than the heat-sensitive member (10) and a linear expansion coefficient approximate to the linear expansion coefficient of the heat-sensitive member (10). For example, the heat-sensitive member (10) is formed of mullite, and the thermally uniformizing member (30) is formed of aluminum nitride, whereby damage caused by thermal expansion can be prevented and at the same time the base portion (11) of the heat-sensitive member (10) can be thermally uniformalized.
