Abstract: A filter material in which protrusions are formed on the surface of a fiber base material by combining the filter base material and particles for forming protrusions having at least a part covered by a photocatalyst or a material containing a photocatalyst is disclosed. A gas treatment apparatus in which a gas treatment filter made of a filter material in which a photocatalyst having a refractive index higher than that of a filter base material is carried on the surface of the filter base material is installed in atmosphere to be treated and ultraviolet rays introduced into the light guiding member are leaked from the photocatalyst, thereby treating gas by the photocatalytic reaction.