FAR-INFRARED RAY TRANSMISSION MEMBER AND METHOD FOR MANUFACTURING FAR-INFRARED RAY TRANSMISSION MEMBER

To appropriately suppress reflection of far-infrared rays, and appropriately form an antireflection film. A far-infrared ray transmission member (20) includes a base material (30) that transmits far-infrared rays, and a functional film (32) that is formed on the base material (30) and includes a low refractive index layer (34) containing oxide as a principal component and having a refractive index equal to or smaller than 1.5 with respect to light at a wavelength of 10 um. The low refractive index layer (34) contains MgO as a principal component, and a content of MgO is equal to or larger than 50 mass% and equal to or smaller than 100 mass% with respect to the entire low refractive index layer (34).