The problem to be solved by the present disclosure is to provide a rubber composition that achieves both thermal degradation resistance and breaking resistance. The solution is a rubber composition including a diene-based rubber (A), a heterocyclic compound (B) having a six-membered aromatic heterocyclic ring, a metal salt (C) (excluding metal oxides, metal carbonate salts, and metal salts of fatty acids with 10 or more carbon atoms), an organic peroxide (D), and a carbon black (E). The mass ratio (D/C) of the organic peroxide (D) to the metal salt (C) is preferably 0.1 to 10.

The problem to be solved by the present disclosure is to provide a rubber composition that achieves both thermal degradation resistance and breaking resistance. The solution is a rubber composition including a diene-based rubber (A), a heterocyclic compound (B) having a six-membered aromatic heterocyclic ring, a metal salt (C) (excluding metal oxides, metal carbonate salts, and metal salts of fatty acids with 10 or more carbon atoms), an organic peroxide (D), and a carbon black (E). The mass ratio (D/C) of the organic peroxide (D) to the metal salt (C) is preferably 0.1 to 10.

A rubber composition comprising a diene-based rubber and a vegetable oil, wherein the vegetable oil is a fatty acid ester triglyceride in which a fatty acid containing at least a saturated fatty acid and an unsaturated fatty acid is ester-bonded to glycerol and has a ratio of the unsaturated fatty acid in the fatty acid of 50 mass % or more, and at least a modified butadiene rubber is contained as the diene-based rubber. It is preferrable that the vegetable oil has a ratio of a polyunsaturated fatty acid in the unsaturated fatty acid of 15 mass % or more. It is preferrable that a content of the vegetable oil is 5 to 30 parts by mass when a total amount of the diene-based rubber is taken as 100 parts by mass.

A rubber composition comprising a diene-based rubber and a vegetable oil, wherein the vegetable oil is a fatty acid ester triglyceride in which a fatty acid containing at least a saturated fatty acid and an unsaturated fatty acid is ester-bonded to glycerol and has a ratio of the unsaturated fatty acid in the fatty acid of 50 mass % or more, and at least a modified butadiene rubber is contained as the diene-based rubber. It is preferrable that the vegetable oil has a ratio of a polyunsaturated fatty acid in the unsaturated fatty acid of 15 mass % or more. It is preferrable that a content of the vegetable oil is 5 to 30 parts by mass when a total amount of the diene-based rubber is taken as 100 parts by mass.