Provided is a method for manufacturing a film-wrapped electrical device, including: a first injection step of depressurizing, to a given pressure lower than atmospheric pressure, the inside of an injection chamber (2) in which a bag-shaped laminate film wrapping member (29) is placed, the laminate film wrapping member (29) having an opening portion (29a) and housing an electrode assembly (21′) including a positive electrode and a negative electrode stacked with a separator therebetween, and injecting part of a predetermined injection amount of an electrolyte solution (20) into the wrapping member (29) through the opening portion (29a); and a second injection step of, after the first injection step, pressurizing the inside of the injection chamber (2) to a pressure higher than the given pressure and injecting the rest of the predetermined injection amount of the electrolyte solution (20).