To provide a method and a device for manufacturing a power storage device constituted by a material having flexibility as an outer coating material, which can reduce a time taken to impregnate an electrolyte in a space of an electrode structure formed by laminating or winding a positive electrode and a negative electrode through a separator.

In a method for manufacturing a laminate type lithium ion secondary battery which houses an electrode structure 10 using an outer coating material 20 having flexibility, the electrode structure 10 is housed in an inner space surrounded by the outer coating material 20 and an electrolyte is injected through the opening of the outer coating material 20. After this, the outer coating material 20 in a restrained state is housed in a pressure container, and the pressure of the inner space and the outer space of the outer coating material 20 is decreased so as to be changed from atmospheric pressure to a vacuum state while the pressure of the outer space of the outer coating material 20 is increased so as to be changed from a vacuum state to atmospheric pressure, which is performed repeatedly so as to impregnate an electrolyte in a space of the electrode structure 10.