PURPOSE: To provide a lead-acid battery hardly causing self discharge by improving a lead-acid battery plate formation method.

CONSTITUTION: A current supply idle period with 30 minutes as the greatest lower bound is set in the early stage of a current supply in the case of plate formation, and during the current supply idle period, extremely weak discharge is carried out in an electric current of 10-l00μA/g per an active material. By means of this this method, low lead oxide in a lead acid battery plate can be reduced, and a discharge capacity maintaining rate of the lead-acid battery can be also heightened.