There is provided a means capable of suppressing generation of a lithium dendrite at the time of charging and discharging while sufficiently suppressing an amount of gas generated at the time of initial charging of an electric device.When a lithium ion is doped in advance to a negative electrode active material, which is used in an electric device including a positive electrode and a negative electrode, after performing a pre-doping step of doping the lithium ion to a negative electrode active material to be doped to reduce a potential (vs. Li+/Li) of the negative electrode active material to be doped with respect to a lithium metal, a dedoping step of dedoping the lithium ion from the negative electrode active material doped with the lithium ion in the pre-doping step to increase a potential (vs. Li+/Li) of the negative electrode active material with respect to the lithium metal is performed.