To provide an infrared ray source capable of being manufactured easily and accurately and causing no deterioration in radiation efficiency.

An infrared ray source 101 includes a heating element 15 and a radiator 23 having an outermost surface formed of a first metal layer L21, and radiates an infrared ray having a peak at a predetermined wavelength. A plurality of micro cavities MC having a diameter size of a wavelength order and a cylindrical form are arranged on a surface of the first metal layer L21, and, when the radius and the depth of the cylinder of the micro cavities MC are denoted as R and D, respectively, D/2R is in the range from 0.3 to 0.7.