An adhesive agent produced by crosslinking an adhesive agent composition containing a polyester resin (i) having a structural portion derived from a polycarboxylic acid compound (a) and a structural portion derived from a polyol component (b), wherein the polyester resin (i) contains a structural portion derived from at least one selected from the group consisting of a dimer acid compound, a sebacic acid compound, and a dimer diol in a proportion of not less than 60 wt. % based on the weight of the polyester resin (i), wherein the polyol component (b) includes a glycol (b1) having an even carbon number (excluding the dimer diol), wherein the polyester resin (i) has an ester group concentration of not less than 2 mmol/g. The adhesive agent has an adhesive force (α) of not less than 1 N/25 mm as measured under predetermined conditions.