An electrochemical device capable of improving arrangement efficiency of bonded bodies and securing favorable sealing characteristics is provided. An electrolyte membrane 11 has a reaction region 11A sandwiched between a fuel electrode 12 and an oxygen electrode 13 and a peripheral region 11B exposed from between the fuel electrode 12 and the oxygen electrode 13. A connection member 20 has a bent section 23 between two flat sections 21 and 22. Since an adhesive layer 14 is provided in the peripheral section 11B of the electrolyte membrane 11, and the bent section 23 of the connection member 20 is bonded to the adhesive layer 14, arrangement efficiency of a bonded body 10 is improved, and favorable sealing characteristics are secured. The adhesive layer 14 has a structure in which a first contact layer having high adhesion to the electrolyte membrane 11, a barrier layer, a strength retention layer, and a second contact layer having high adhesion to the connection member 20 are sequentially laminated. Since a connection-member-side adhesive layer is provided on the bent section 23 of the connection member 20, adhesion strength can be further improved.