ELECTROCHEMICAL DEVICE

To provide an electrochemical device that easily achieves a thickness reduction of its insulating sealing member and can have improved performance. In an electrochemical device of an embodiment, a cell stack has an insulating sealing member installed between a first separator and a second separator and configured to seal a gap between the first separator and the second separator and electrically insulate the first separator and the second separator from each other. The insulating sealing member has a metal layer and an insulation layer stacked on the metal layer in a stacking direction. The insulation layer contains a glass paste base material having a lower glass transition temperature than an operating temperature of the cell stack and a filler material having a higher glass transition temperature than the operating temperature of the cell stack, and the filler material is dispersed in the glass base material.