PURPOSE: To detect the direction of a heat source even when the heat source can not be directly viewed and to reduce erroneous operation due to a wind carrying no heat, by selectively taking out the detection signals of the heat-sensitive elements mounted to a plurality of radially partitioned sensing chambers.

CONSTITUTION: A cylindrical sensing part has opening parts provided to the center of the upper part and side surface thereof to permit the free flow of the open air. The cylindrical interior of said sensing part is partitioned by partition walls (a) radially extending from the center axis thereof to form a plurality of sensing chambers. A plurality of temp.-sensitive elements (c) are respectively mounted to each of the sensing chambers so as to form axial symmetric relation. When heated air flows in the direction shown by an arrow, said air flows out from the opening parts (b) of the right-hand side surface. Therefore, difference is generated between the detection temps. of two temp.-sensitive elements (c) provided in axially symmetric relation on the windward and the leeward. Hereupon, the detection signals of a plurality of the temp.-sensitive elements (c) are taken out by a multiplexer and the direction of a hot air flow is calculated on the basis of the detection signals of a plurality of the temp.-sensitive elements (c) by a central processing unit and the result thereof is displayed on a display part.