Provided is an adhesive composition leading to sufficient adhesive strength when used for bonding to a polyolefin resin molded article that bonds poorly with other members. Also provided is an adhesive composition having excellent heat resistance (heat resistant adhesion) in the bonded part of a composite body obtained by joining a polyolefin resin-formed body and other member. This adhesive composition contains an organic solvent, a carboxyl group-containing polyolefin resin which is dissolved in this organic solvent and which has a melt flow rate of 5 to 40 g/10 min when measured at 130° C., and a polyfunctional isocyanate compound. This adhesive composition may further contain a carboxyl group-containing polyolefin resin having a melting point of 120° C. to 170° C.