A thermoplastic elastomer composition that exhibits excellent rubber elasticity, etc. is obtained by dynamically heating a polymer composition in the presence of the crosslinking agent, the polymer composition including an α-olefin thermoplastic resin (A), and an oil-extended ethylene copolymer (B) that includes an ethylene copolymer that satisfies given conditions, and 50 to 150 parts by mass of a first mineral oil-based softener based on 100 parts by mass of the ethylene copolymer, the content of the oil-extended ethylene copolymer (B) being 30 mass % or more based on the total amount (=100 mass %) of the polymer component including the α-olefin thermoplastic resin (A) and the oil-extended ethylene copolymer (B).