An infrared conversion device includes: a substrate (122); and a metal fine particle layer (123) formed on the substrate (122), wherein the metal fine particle layer (123) is formed with metal fine particles (124) and a dielectric material (125) that fills gaps between the metal fine particles (124) and absorbs incident infrared rays. Alternatively, an infrared conversion device detects infrared rays converted into visible light by detecting a change caused in the permittivity of a light receiving material (125) by infrared absorption as a change in the intensity of scattering light based on local plasmon resonance.