A method for charging a lithium ion secondary battery including at least a positive electrode, a negative electrode provided with a negative electrode active material layer that includes carbon as a negative electrode active material, an electrolytic solution, and a sheathing material that encloses the positive electrode, the negative electrode and the electrolytic solution; the negative electrode active material layer including carboxymethyl cellulose and the electrolytic solution including an additive that can be decomposed at a predetermined voltage includes: preliminary charging including constant-current charging in which charging is performed at a fixed current value and, following the constant-current charging, constant-voltage charging in which charging is performed at a fixed voltage; degassing in which gas is removed from within the sheathing material after the preliminary charging; and main charging that follows the degassing in which the lithium ion secondary battery is charged. The fixed voltage during the constant-voltage charging is at least 3.3 V per cell.