Abstract: To provide a rubber composition excellent in elasticity and low loss property. A rubber composition comprising 100 parts by weight of a chloroprene rubber and from 1.2 to 3.0 parts by weight of cellulose nanofibers, characterized in that a vulcanized sheet obtained by vulcanizing the rubber composition has a 100% tensile stress (M100) increased by 1.5 MPa or more per part by weight of the cellulose nanofibers added, where the increase of M100 is calculated by subtracting M100 of a vulcanized sheet containing no cellulose nanofibers from M100 of the vulcanized sheet containing the cellulose nanofibers, and dividing the difference by the amount of the cellulose nanofibers contained.