PURPOSE: To obtain a thermoplastic elastomer exhibiting rubber elasticity over a wide temperature range, having excellent thermal creep resistance and useful for domestic appliance parts, etc., by carrying out dynamic heat-treatment of a rubber containing unsaturated carbon double bond group, a polyolefin resin, a specific cross-linking agent and an organic peroxide catalyst.

CONSTITUTION: This elastomer is produced by the dynamic heat-treatment of (A) 100 pts.wt. of a rubber containing unsaturated carbon double bond group such as natural rubber, (B) preferably 5-30 pts.wt. of a polyolefin resin such as PE, (C) preferably 0.005-30 pts.wt. of an organic organosiloxane cross-linking agent having two or more SiH groups in the molecule and (D) preferably 0.0001-2 pts.wt. of an organic peroxide catalyst such as 2,5-dimethyl-2,5-di(t- butylperoxy)hexane.