A urethane-based adhesive composition, comprising: a urethane-based prepolymer; a first adhesion promoter; and a second adhesion promoter, wherein the urethane-based prepolymer is prepared from a first polyol compound, a second polyol compound, a third polyol compound, a polyolefin diol and an isocyanate-based compound; each of the first polyol compound and the second polyol compound comprises 3 to 10 hydroxyl groups per molecule; the first polyol compound has a larger weight-average molecular weight than the second polyol compound; the first polyol compound has a weight-average molecular weight of 4,500 g/mol to 8,000 g/mol determined as set out in the description; the third polyol compound comprises two hydroxyl groups per molecule and has a repeating unit of a main chain having 2 or 3 carbon atoms; the polyolefin diol has a linear repeating unit of a main chain having 4 to 10 carbon atoms and a number-average molecular weight of 500 g/mol to 2,700 g/mol determined as set out in the description; the urethane-based adhesive composition comprises 5 parts by weight to 15 parts by weight of the first polyol compound, 6 parts by weight to 15 parts by weight of the second polyol compound, 3 parts by weight to 15 parts by weight of the third polyol compound, and 1 part by weight to 5 parts by weight of the polyolefin diol the first adhesion promoter is a polyisocyanate-based compound; the second adhesion promoter is a silane-modified compound; and the urethane-based adhesive composition comprises 5 parts by weight to 15 parts by weight of the second adhesion promoter with respect to 100 parts by weight of the urethane-based prepolymer. a urethane-based prepolymer; a first adhesion promoter; and a second adhesion promoter, wherein the urethane-based prepolymer is prepared from a first polyol compound, a second polyol compound, a third polyol compound, a polyolefin diol and an isocyanate-based compound; each of the first polyol compound and the second polyol compound comprises 3 to 10 hydroxyl groups per molecule; the first polyol compound has a larger weight-average molecular weight than the second polyol compound; the first polyol compound has a weight-average molecular weight of 4,500 g/mol to 8,000 g/mol determined as set out in the description; the third polyol compound comprises two hydroxyl groups per molecule and has a repeating unit of a main chain having 2 or 3 carbon atoms; the polyolefin diol has a linear repeating unit of a main chain having 4 to 10 carbon atoms and a number-average molecular weight of 500 g/mol to 2,700 g/mol determined as set out in the description; the urethane-based adhesive composition comprises 5 parts by weight to 15 parts by weight of the first polyol compound, 6 parts by weight to 15 parts by weight of the second polyol compound, 3 parts by weight to 15 parts by weight of the third polyol compound, and 1 part by weight to 5 parts by weight of the polyolefin diol the first adhesion promoter is a polyisocyanate-based compound; the second adhesion promoter is a silane-modified compound; and the urethane-based adhesive composition comprises 5 parts by weight to 15 parts by weight of the second adhesion promoter with respect to 100 parts by weight of the urethane-based prepolymer.