Provided are inorganic fibers which can exhibit high biosolubility and have excellent heat resistance as the constituting material for a filter material, a sealing material or the like, while exerting minimized effects on the human body or the living environment even when the fibers have an average diameter of 1 μm or less. Inorganic fibers including 35 mass% to 88 mass% of Al2O3, 3 mass% to 45 mass% of CaO and 5 mass% to 40 mass% of SiO2, wherein the total content of Al2O3, CaO and SiO2 is 98 mass% or more of the entire fibers.