To provide an electrochemical device which is free of a short-circuit problem between positive and negative electrodes and prevents formation of an electrolyte non-injected portion, making the device excel in electrolyte injection properties.

The electrochemical device comprises an electrode group composed of a cathode and an anode which are alternately laminated and an electrolyte, and further includes a separator between the cathode and the anode. At the top and the bottom of at least one electrode of the cathode and the anode, a first and a second separator larger than the electrode itself are included respectively. The end portions of the second separator exposed from the end portions of the electrode rise from the bottom to the top side and are joined with the end portions of the first separator each other to form junctions, whereby a bag-shaped separator is formed. The junctions formed in the bag-shaped separator are located above the top face of the electrode, so that they do not touch part of another bag-shaped separator adjacent thereto.