An adhesive sheet which comprises at least a substrate and an adhesive layer, wherein the substrate has a substrate layer, a load at the time of 5% elongation of the substrate is 15 N/cm or less, a stress relaxation rate of the substrate by elongating to 10%, stopping the elongation at that state and after lapsing 600 seconds is 40% or more and 100% or less, and a chemical weight increased ratio of the substrate is 60% or less, wherein the substrate layer contains at least a urethane-based polymer and the urethane-based polymer constituting the substrate layer is an ester-based thermoplastic polyurethane, wherein the ester-based thermoplastic polyurethane is at least one selected from the group consisting of an adipate-ester-based thermoplastic polyurethane and a polycaprolactone-ester-based thermoplastic polyurethane, wherein the substrate has a surface protective layer and a substrate layer, and the surface protective layer is provided at the outermost surface of the adhesive sheet; and wherein the surface protective layer comprises an acrylic-based resin, a fluorine-based resin or a urethane-based polymer, the resin components occupying 50% by weight or more in the surface protective layer after the formation thereof; wherein the load at the time of 5% elongation of the substrate is determined as follows: (i) an acrylic-based adhesive layer with a thickness of 50 μm is formed on one of the surfaces of the substrate to prepare an adhesive tape, provided that in the case of the substrate having a substrate layer and a surface protective layer, the adhesive layer is formed onto the substrate layer; (ii) this adhesive tape is cut to a width of 10 mm and a length of 160 mm; (iii) a tensile test is carried out with a tensile rate of 200 mm/min, a distance between chucks of 100 mm at 23°C to obtain a stress-strain curve; and (iv) the load at the time of 5% elongation of the adhesive sheet is obtained; wherein the stress relaxation rate of the substrate is determined as follows: (i) an acrylic-based adhesive layer with a thickness of 50 μm is formed on one of the surfaces of the substrate to prepare an adhesive sheet, provided that in the case of the substrate having a substrate layer and a surface protective layer, the adhesive layer is formed onto the substrate layer; (ii) this adhesive sheet was cut to a width of 10 mm and a length of 160 mm, and at a tensile rate of 200 mm/min and a distance between chucks of 100 mm at 23°C, it was continued to tension until the distance between chucks became 110 mm and stopped at 10% elongated state; (iii) the load (residual stress) after lapsing 600 seconds from the stopping was measured, and the stress relaxation rate was obtained by using the following calculation formula: Stress relaxation rate (%) = {(load at 10% elongation - load at 10% elongation after lapsing 600 seconds)/load at 10% elongation} × 100; and the chemical weight increased ratio of the substrate is determined as follows: (i) the substrate is cut to a width of 30 mm and a length of 30 mm to prepare a sample for measurement; (ii) the sample for measurement is dipped into an organic solvent in which regular gasoline and ethanol has been mixed with a ratio of 90% by weight/10% by weight; (iii) the weight after lapsing 30 minutes is measured; and (iv) the increased ratio of the weight of chemicals is obtained by using the following calculation formula: Weight increased ratio (%) = {(Weight after 30 minutes from dipping into chemicals - Weight before dipping)/Weight before dipping} × 100;.