Disclosed is an oxide catalyst for use in catalytic oxidation or ammoxidation of propane or isobutane in the gaseous phase, which comprises a composition represented by the Mo1VaSbbNbcZdOn (wherein: Z is at least one element selected from the group consisting of tungsten, chromium, titanium, aluminum, tantalum, zirconium, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, zinc, boron, indium, germanium, tin, lead, bismuth, yttrium, gallium, rare earth elements and alkaline earth metals; and a, b, c, d, and n are, respectively, the atomic ratios of V, Sb, Nb, Z and O, relative to Mo), wherein 0.1≦a