There is provided an infrared light source that has a simple structure and radiates infrared rays polarized in a specific direction and having a specific wavelength. The infrared light source (100) comprises a heat generator (107) and a latticework (101) in which a dielectric part (105) and a metal part (103) are alternately formed at a constant pitch in a constant direction. The infrared rays are radiated in a direction perpendicular to the surface of the latticework and are polarized in the direction indicated by an arrow A. If the constant pitch is denoted by P, the width of the dielectric part in the constant direction by T, and the specific wavelength by λ, for arbitrary P and T that meet the inequalities 0