It is an object of the present invention to provide a rubber composition having: excellent sealing properties, heat resistance and acid resistance; a low reaction force, low hardness and low compression set; and excellent low-temperature recovery properties that contribute to sealing properties particularly in low-temperature environment. It is another object of the invention to provide uses of the rubber composition and main bodies on which the rubber composition has been mounted. The rubber composition of the present invention comprises a specific ethylene/α-olefin/non-conjugated polyene copolymer [A], a SiH group-containing compound [B] having two SiH groups in one molecule, and a SiH group-containing compound [C] having three SiH groups in one molecule.