PURPOSE: To prevent the generation of the measuring error of a sensor or the destruction thereof, by coating a thermopile, which is provided to the surface of a thin plate in the side opposite to a surface to which heat flux is incident, by using an insulating resin.

CONSTITUTION: The thermopile 4, which is attached to the surface of a thin plate 1 through insulating layer 3 in the side opposed to the heat sink 2 provided in the side opposite to a surface to which heat flux is incident, is coated with a resin 11. This resin layer 11 may be one filling the whole of the cavity in the heat sink and, when the heat conductivity thereof is made low and the thickness thereof is increased, the deformation of each part of the resin layer 11 is suppressed and the release thereof can be prevented. As a result, the release of the thermopile 4 from the thin plate 1 or the destruction thereof can be prevented.