The present invention relates to an olefinic thermoplastic elastomer composition obtainable by dynamically heat treating 5 to 50 parts by weight of a polypropylene resin (A) and 50 to 95 parts by weight of an null-olefinic copolymer (B) having a Mooney viscosity ML1null4 (100null C.) of 60 to 250 in the absence of a crosslinking agent. The olefinic thermoplastic elastomer composition is characterized in that the glass transition temperature (Tg) in dynamic visco-elasticity measurement derived from the polypropylene resin (A) is lower than that of the polypropylene resin (A) itself and that the null-olefinic copolymer (B) is at least one selected from the following (b-1) and (b-2): (b-1) ethylene-null-olefinic copolymers which have an ethylene content of 51 to 60 mol % to the total amount of the ethylene-null-olefinic copolymer-constituting ethylene and null-olefin other than ethylene, (b-2) propylene-null-olefini ccopolymers which have a propylene content of 60 to 90 mol % to the total amount of the ethylene-null-olefinic copolymer-constituting propylene and null-olefin other than propylene.