Abstract: An alkaline storage battery with improved cycle life and self-discharge characteristics is disclosed. The battery comprises a positive electrode, a negative electrode, a separator and an alkaline electrolyte. For the separator, a material of a woven or nonwoven fabric sheet or a porous film of polyolefine resin of which surfaces have been modified with a hydrophilic compound having a carboxyl group by graft-polymerization. The quantity of carbonates inside the battery is regulated to 150 mg/Ah battery capacity. The quantity of carbonates inside the battery can be regulated to a minimum by optimizing graft polymerization and subsequent washing conditions.