An infrared detector (10) which converts entering infrared IR into light in a different wavelength band, and which detects the converted light in the different wavelength band includes: a convex-concave structure (28) provided on a light acceptance surface of the infrared detector (10); and a metal film (24) provided on an outer circumferential face of the light detector (10) other than the light acceptance surface thereof, the metal film (24) covering the outer circumferential face. In the infrared detector (10), light which enters the light detector (10) after passing through the corvex-concave structure (28) and the converted light in the different wavelength band are confined inside the light detector (10): by causing the entering light to be reflected on the metal film (24) ; by causing light reflected on the metal film (24) to be reflected on the convex-concave structure (28); and by causing the converted light in the different wavelength band to be reflected between the metal film (24) and the convex-concave structure (28).
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