To surely preclude a battery having a defect as a micro short circuit and the like from the terminal voltage at the initial charge.

In the initial charging method of the secondary battery, the terminal voltage of each battery is measured after a lapse of a preset criterion time after the start of the initial charge with a constant current, the battery of which the terminal voltage does not reach a predetermined voltage is defined as a defective product, and the charge to the defective product is stopped.