A rubber composition consisting essentially of 5-99 parts by weight of a thermosetting resin and 94-1 parts by weight of one of the following functional rubber-like copolymers (I) to (III) having a Mooney viscosity ML.sub.1+4.sup.100 of 20-120:(I) a functional rubber-like copolymer consisting of 1-20% by weight of a monomer having epoxy groups, hydroxyl groups or amino groups, 15-50% by weight of acrylonitrile and 40-80% by weight of butadiene and/or isoprene as monomer units constituting the polymer,(II) a functional rubber-like copolymer consisting of 1-20% by weight of a monomer having epoxy groups, hydroxyl groups or amino groups, 40-99% by weight of an alkyl (meth)acrylate and/or an alkoxyalkyl (meth)acrylate and 0-30% by weight of monomers copolymerizable therewith other than butadiene and isoprene, as the monomer units constituting the polymer, and(III) a functional rubber-like copolymer consisting of 1-20% by weight of a monomer having epoxy groups, hydroxyl groups or amino groups, 15-50% by weight of acrylonitrile, 20-60% by weight of butadiene and/or isoprene and 5-65% by weight of an alkyl (meth)acrylate and/or an alkoxy (meth)acrylate as the monomer units constituting the polymer.Said functional rubber copolymer may include 10% by weight or less of a polyfunctional monomer as a monomer unit constituting the polymer. In this case, the ratio of the thermosetting resin to the functional rubber-like copolymer is 50-99 parts by weight of the former to 1-50 parts by weight of the latter.