An adhesive agent having excellent bonding properties with oxide films and excellent heat-dissipation properties and a connection structure using the same. The adhesive agent contains an epoxy compound, a cationic catalyst, and an acrylic resin containing acrylic acid and acrylic acid ester having a hydroxyl group. Acrylic acid in the acrylic resin reacts with the epoxy compound to generate connections between an island of acrylic resin and a sea of epoxy compound and roughen the surface of an oxide film to improve an anchor effect with the sea of epoxy compound; solder particles contained in the adhesive agent are melted to form metal bonding with an electrode, thereby enabling improvement in adhesive strength between the adhesive agent and the electrode and further improving heat dissipation from a surface of the metal bonding.