PURPOSE: A rubber composition, prepared by incorporating a rubber-like elastic material with a granular or powdery novel phenol-aldehyde resin containing nitrogen, having improved storage stability and fluidity characteristics and further reactivity, and suitable for molding materials.

CONSTITUTION: A composition prepared by incorporating (A) 100pts.wt. rubber- like elastic material, preferably a silicone rubber, with (B) 200pts.wt. or less granular or powdery phenol-aldehyde resin, containing nitrogen, obtained by condensing (i) a phenol, preferably phenol, with (ii) a nitrogen compound, e.g. urea, having two or more active hydrogen atoms, and (iii) an aldehyde, containing spherical primary particles having 0.1W100microns particle diameter and secondary aggregates thereof, having 0.1W2 ratio between the maximal absorption intensity (D1450W1500) at 1450W1500cm-1 wave number and the maximal absorption intensity (D960W1020) at 960W1020cm-1 wave number in an infrared absorption spectrum measured by the KBr tablet method.