To provide a method for producing an unsaturated nitrile, capable of efficiently producing an unsaturated nitrile without using a halogen promoter, by subjecting propane or isobutane to ammoxidation reaction in the presence of a specific catalyst composition.

This method for producing an unsaturated nitrile comprises subjecting propane or isobutane to ammoxidation reaction in the presence of a catalyst composition expressed by the formula: FeaSbbCrcModQeOf {Q is one or more elements selected from a group comprising Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Pr, Nd, Sm, Th, U, Ti, Zr, Hf, Nb, Ta, W, V, Mn, Re, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Tl, Ge, Sn, Pb, P, B, As, Bi, Se and Te; (a) to (f) express each an atomic ratio of each element and satisfy (a)=5-15, (b)=5-100, (c) and (d) are each 0.01-5, (e)=0-15, (f) is a number corresponding to an oxide to be formed} (for example, a composition containing iron antimonate, such as FeSbO4).