This method for manufacturing an electrochemical device is characterized in that in a step for producing a positive electrode wherein a positive electrode layer containing a conductive polymer is formed on a first collector and/or in a step for producing a laminate wherein a separator is interposed between a positive electrode and a negative electrode, the positive electrode and/or the laminate ismaintained in a reduced pressure atmosphere, and a gas mainly composed of CO2 is subsequently introduced into the reduced pressure atmosphere.