The present invention includes: a first charging step for charging at a first C-rate from an initial charging voltage to a first charging voltage; and a second charging step for completing a charging process so as to reach a target voltage, after reaching the first charging voltage, by gradually decreasing the C-rate within a range not exceeding the first C-rate. The method for charging a secondary battery according to the present invention is capable of preventing the battery from deteriorating and thus improving the lifespan of the battery.