The purpose of the present invention is to provide: a polyester-based pressure-sensitive adhesive layer, for which a pressure-sensitive adhesive composition (pressure-sensitive adhesive solution) without any acrylic pressure-sensitive adhesive or the like which needs a large amount of an organic solvent and is difficult to apply thickly; to provide a polyester-based pressure-sensitive adhesive layer that is friendly to the global environment, can be applied thickly, has a high level of cost effectiveness and workability, and also has a high level of adhesion, retention, and repulsion resistance; and to provide a pressure-sensitive adhesive tape or double-sided pressure-sensitive adhesive tape having such a pressure-sensitive adhesive layer. The invention is directed to a polyester-based pressure-sensitive adhesive layer including a product made from a polyester-based pressure-sensitive adhesive composition including: a polyester obtained by polycondensation of at least a dicarboxylic acid component and a diol component; and a tackifier, the polyester-based pressure-sensitive adhesive layer having a gel fraction of 15% by weight or more to less than 40% by weight.