PURPOSE: To obtain a high-viscosity liquid or solid adhesive composition, having excellent mixing and deodorizing operability and capable of preventing deterioration, by adding and reacting a mixture of polyols with a tackifier with a polyisocyanate compound.

CONSTITUTION: A liquid or solid adhesive composition, obtained by adding and reacting (A) a polyisocyanate compound normally while heating with (A) a mixture of (i) polyols with (ii) a tackifier consisting of a polymer, such as polystyrene based polymer, preferably without substantially containing functional groups reactive with isocyanate groups in an amount of 20W120wt.% based on the component (i), containing polyurethane prepolymer and having preferably ≥100,000cP viscosity at 25°C.