PURPOSE: To measure exactly the amount of a heat current flowing through a surface by controlling said amount so that the temp. difference between the temp. of an area to which a heat resistance plate is provided and that to which said plate is not provided becomes zero in a surface of an exothermic or endothermic material.

CONSTITUTION: On a surface 2 of the exothermic or endothermic material 1, the temp. difference ΔT2 between a position P1 to which the heat resistance plate 3 is provided and a position P2 to which it is not provided is detected by a temp. difference detecting means 22, an output S2 is inputted into a driving control circuit 21, and a heating and cooling plate 20 is controlled by a driving control output D so that the ΔT2 attains to zero. Under this state, the temp. difference ΔT1 between two positions in the depth direction of the plate 3 are detected by a temp. difference detecting means 4 having thermometer resistance elements 6, 7, and a measured result of a heat current amount Q passing through the area to which the plate 3 is provided is obtained by a treating device 5. The heat current amount Q can be measured under the equal state to the temp. of the surface 2 in case that the plate 3 is not provided at the surface.