To provide an electrochemical device with a layer structure causing no deterioration of characteristics of materials, in the method for preparing an electrochemical device comprising a first current collector, a first electrode active material layer, a solid electrolyte layer, a second electrode active material layer and a second current collector, all of which are accumulated, the first electrode active material layer, the second electrode active material layer or the solid electrolyte layer is formed by supplying atoms, ions or clusters constituting the first electrode active material layer, the second electrode active material layer or the solid electrolyte layer to the substrate, while irradiating electrons or electromagnetic waves with energy prescribed according to the composition of the first electrode active material layer, the second electrode active material layer or the solid electrolyte layer.