Disclosed is a thermoplastic elastomer composition which is excellent in a vibration-proof property and a sound-proof property, and which has flexibility, wear resistance and processability at the levels required for a member (e.g., a roller) to be used in an image-forming device (e.g., a printer). The thermoplastic elastomer composition contains a butyl rubber at a ratio of 30 to 80 mass % (inclusive), and further contains 15 to 50 parts by mass (inclusive) of an olefin thermoplastic resin and 10 to 100 parts by mass (inclusive) of a hydrogenerated styrene thermoplastic elastomer relative to 100 parts by mass of the rubber component, wherein the rubber component is finely dispersed by dynamic cross-linking.