To produce a modified resin excellent in low-temperature sealing property, adhesive strength and liquid stability in long-term storage and further provide a resin composition dissolved or dispersed in an organic solvent without using an aromatic hydrocarbon which becomes a problem on operation environment.

The adhesive composition dissolved or dispersed in an organic solvent is obtained by dissolving a modified resin obtained by mixing (A) a crystalline propylene-α-olefin-based copolymer containing 50-85 mol% propylene component and having ≥50% degree of crystallinity measured by X ray diffraction method with (B) a amorphous polypropylene-α-olefin copolymer containing ≥90 mol% propylene component and having ≤10% degree of crystallinity measured by X ray diffraction method and carrying out graft polymerization of the mixture with an unsaturated carboxylic acid or its anhydride and dissolving the resultant modified resin in an organic solvent under heating and adding an amine compound to the solution.