In an electrochemical device having an element main body 1A enclosed in an exterior package 1B, a peripheral region of the exterior package 1B is provided with an elastic structure or a plurality of elastic structures R1, R2 having an elastic force in a thickness direction (Z-axis direction) of films. Each of the elastic structures R1, R2 has a first region of the exterior package 1B folded along a film outer edge, and a second region of the exterior package 1B opposed to the first region. Two ends R11, R13 (R21, R23) of the first region in a direction along the film outer edge are in contact with the second region, and between the two ends R11, R13 (R21, R23) there is a space (with a maximum height 2R) between the first region and the second region.