An electrochemical device, which can be thin enough to be built into a thin electronic device, and a method for manufacturing the same. The electrochemical device has: an element body on which a pair of internal electrodes are laminated so as to sandwich a separator sheet; an outer sheet covering the element body; sealing parts for sealing the peripheral edge of the outer sheet so that the element body is immersed in an electrolyte solution; and lead terminals electrically connected to either one of internal electrodes and leading out from the sealing parts of the outer sheet. At least a portion of a resin tape constituting the sealing parts, from which the lead terminals lead out, is thermally fused to an inside layer made from resin, which is present on the inner face of the outer sheet, in a position that does not overlap with the internal electrodes.