For the production of acrylonitrile by ammoxidation of propylene, there is provided a process capable of giving a high yield and maintaining such an effect for a long period of time. In producing acrylonitrile by ammoxidation of propylene, a fluidized bed catalyst is used and the reaction is carried out while appropriately adding a molybdenum-containing material, wherein the fluidized bed catalyst contains molybdenum, bismuth, iron, nickel, chromium, potassium, an F component and silica as essential components, and has a number of Mo/Me of from 0.8 to 1, wherein the Mo/Me is a number obtained by dividing the product 20 of a valence number of molybdenum as molybdic acid and an atomic ratio of molybdenum by the sum of respective products of respective valence numbers and atomic ratios of bismuth, iron, nickel, chromium, potassium, the F component element, a G component element and a Y component element.