An infrared ray sensing element, includes: 1) a semiconductor substrate; 2) an infrared ray receiver disposed above the semiconductor substrate in such a manner as to be isolated from the semiconductor substrate, the infrared ray receiver being configured to receive an infrared ray; and 3) a beam configured to support the infrared ray receiver to the semiconductor substrate and include a thermopile configured to sense a temperature increase of the infrared ray receiver, wherein one of the following has a cross sectional shape that includes at least one protruding part: i) the beam, and ii) the thermopile.