To provide an olefin elastomer which exhibits an improved strength of adhesion to an ethylene-propylene rubber and thus can give a durable product by compounding a thermoplastic olefin elastomer with a specified amount of a low-density polyethylene.

This olefin elastomer for adhesion molding is prepared by mixing 100 pts.wt. thermoplastic olefin elastomer with 5-30 pts.wt. low-density polyethylene (e.g. a linear low-density polyethylene). An ethylene-propylene rubber sheet vulcanization-molded into a certain shape as an adherend is made into a shape of a long strip and is set in a metal mold, and the above-prepared olefin elastomer for adhesion molding is injected into the mold at specified injection pressure, cylinder temperature, etc., thus giving an adhesion-molded thermoplastic olefin elastomer/ethylene-propylene rubber article. The adherend may be a solid or foamed ethylene/propylene rubber.