Provided is a thermoplastic elastomer composition obtained by melt-kneading (A) an ethylene/α-olefin/non-conjugated polyene copolymer rubber that is a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms and a non-conjugated polyene, (B) a polyolefin resin and (C) a mineral oil-based softening agent in the presence of (D) a crosslinking agent, at least part of the ethylene/α-olefin/non-conjugated polyene copolymer rubber (A) being crosslinked, the thermoplastic elastomer composition having a sea-island structure in which the ethylene/α-olefin/non-conjugated polyene copolymer rubber (A) is dispersed as a dispersed phase (island phase) in a continuous phase (sea phase) of the polyolefin resin (B), and when a cross-section of the composition is observed with an atomic force microscope (AFM), a ratio of (b) a local elastic modulus of the continuous phase to (a) a local elastic modulus of the dispersed phase being from 10 to 30.