The method for manufacturing a thermoplastic elastomer composition of the present invention comprises continuously feeding a mixture comprising pelletized olefinic resin (A), a pulverized product (B) obtained by pulverizing bulk olefinic rubber, and a crosslinking agent (C) into a continuous kneading machine, and performing a dynamic heat treatment to yield the thermoplastic elastomer composition. An olefinic thermoplastic elastomer composition having excellent tensile characteristics and molded appearance can be manufactured with high productivity by the method of the present invention.