Abstract: An air filter material having the construction of (1) an upper fibrous layer to be disposed at upper-stream position of influent air, containing 50 to 70% by weight of small diameter polyester fiber and 50 to 30% by weight of larger diameter polyester fiber, the basis weight of the layer being 25 to 45 g/m.sup.2 ; (2) an intermediate fibrous layer partially jointed to the upper layer by local intertwinement of fibers, containing 60 to 80% by weight of small diameter polyester fiber and 20 to 40% by weight of larger diameter polyester fiber, the basis weight of the intermediate layer being 40 to 60 g/m.sup.2 ; (3) a lower fibrous layer to be disposed at downstream position of the influent air, which is partially jointed to the intermediate layer by local intertwinement of fibers and which contains 60 to 80% by weight of small diameter rayon fiber and 40 to 20% by weight of larger diameter rayon fiber, the basis weight of the lower fibrous layer being 80 to 100 g/m.sup.