PURPOSE: To provide an adhesive composition capable of firmly bonding a polyolefinic material without pretreating by mixing an isocyanate-containing polyester-based urethane, a chloroprene rubber, a specific silicone and a halogenating agent.

CONSTITUTION: An isocyanate-containing polyester-based urethane is prepared by reacting a polyisocyanate such as 2,4-tolylene diisocyanate and polyesterpolyol such as polybutylene adipate. An adhesive composition is prepared by mixing this urethane with a chloroprene rubber, a silicone which contains a primary amino group in the side chain, such as one represented by the formula, and a halogenating agent such as sodium hypochlorite. This adhesive composition is suitably used for bonding a polyolefinic material difficult to bond which is used as the parts of an automobile.