ELECTROCHEMICAL DEVICE

An electrochemical device can include a membrane electrode assembly (MEA), a separator stacked on the MEA and including a flow path portion provided to face the MEA, a manifold portion through which a reaction fluid can be introduced or discharged, and a through-hole provided between the flow path portion and the manifold portion to guide the reaction fluid, which has passed through the manifold portion, to the flow path portion, and a sealing part selectively separably stacked on the separator and configured to define a connection channel configured to connect the manifold portion and the flow path portion through the through-hole, and the sealing part includes a first elastic sheet, a second elastic sheet stacked on the first elastic sheet, and a reinforcement sheet having relatively higher rigidity than the first elastic sheet and the second elastic sheet and interposed between the first elastic sheet and the second elastic sheet.