The present invention relates to a composition including a β-type iron silicate, which includes all or part of iron in a β-type framework structure, and a solid acidic porous inorganic oxide. The present invention is characterized in that the β-type iron silicate is compounded with the porous inorganic oxide having solid acidic properties so that the solid acidic function derived from aluminum of the β-type iron silicate, is reinforced or complemented by the porous inorganic oxide, the individual particles of which are physically isolated from each other. It is preferred that the fluorine content relative to the dry weight of the β-type iron silicate is 400 ppm or less and the crystal particles of the β-type iron silicate have a truncated square bipyramidal morphology. According to the present invention, a composition that is useful as a high-performance catalyst, adsorbent, or the like, can be provided.