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.