A method for producing a non-aqueous electrolyte secondary battery, comprising the steps of: - placing an electrode body into an outer casing , the electrode body having a folded-separator structure or a wound structure in which a positive electrode including a positive-electrode active material and a negative electrode including a negative-electrode active material are stacked with a separator interposed therebetween; - placing a non-aqueous electrolyte free of a flame retardant into the outer casing; - permeating the non-aqueous electrolyte free of a flame retardant into the positive electrode and the negative electrode placed in the outer casing 17); - charging the electrode body by applying a voltage between the positive electrode and the negative electrode placed in the outer casing ; - placing a flame retardant into the outer casing ; and - sealing the outer casing , wherein the step of placing the flame retardant is a step of placing a non-aqueous electrolyte containing the flame retardant dissolved therein into the outer casing that houses the positive electrode and the negative electrode , into which the non-aqueous electrolyte free of a flame retardant has been permeated, and wherein the step of charging is a step of charging the electrode body with the state in which the surface of the positive-electrode active material and the surface of the negative-electrode active material are in contact with the non-aqueous electrolyte substantially free of the flame retardant , and characterized in that the step of charging is a step of charging the electrode body after the flame retardant is placed into the outer casing . - placing an electrode body into an outer casing , the electrode body having a folded-separator structure or a wound structure in which a positive electrode including a positive-electrode active material and a negative electrode including a negative-electrode active material are stacked with a separator interposed therebetween; - placing a non-aqueous electrolyte free of a flame retardant into the outer casing; - permeating the non-aqueous electrolyte free of a flame retardant into the positive electrode and the negative electrode placed in the outer casing 17); - charging the electrode body by applying a voltage between the positive electrode and the negative electrode placed in the outer casing ; - placing a flame retardant into the outer casing ; and - sealing the outer casing , wherein the step of placing the flame retardant is a step of placing a non-aqueous electrolyte containing the flame retardant dissolved therein into the outer casing that houses the positive electrode and the negative electrode , into which the non-aqueous electrolyte free of a flame retardant has been permeated, and wherein the step of charging is a step of charging the electrode body with the state in which the surface of the positive-electrode active material and the surface of the negative-electrode active material are in contact with the non-aqueous electrolyte substantially free of the flame retardant , and characterized in that the step of charging is a step of charging the electrode body after the flame retardant is placed into the outer casing . <EOS>