To obtain a catalyst capable of remarkably increasing yield of an unsaturated nitril by including a specific metal in the catalyst supported on silica.

This catalyst is supported by 20-60 wt. % silica and components except silica are composed of the formula (X is Te and/or Sb; Z is Ti, W, Cr, Ta, Sn, Y, Yb, La or the like; p, q, r, s, t and n show an atomic ratio based on 1 atom of Mo, 0.1≤p≤0.6, 0.01≤q≤0.6, 0.01≤r≤0.6, 0.001≤s≤0.3, 0≤t≤1; n is an atomic ratio of oxygen determined by oxidation number of a constituted metallic element). The catalyst is used when propane or isobutane is catalytically ammoxidized in vapor phase to give an unsaturated nitril. Preferably the catalyst is prepared using a niobium solution in which molar ratio of dicarboxylic acid to niobium is 1-8. For example, the catalyst can be produced by spray-drying a mixed solution of a raw material containing a catalyst component and burning the resultant dried powder at 500-700°C.