This invention relates to a battery pack composed of a plurality of flat type gas depolarizable galvanic cells such as the zinc-air battery system and its packaging method for such battery pack. More specifically, projections of a certain value of height are formed on at least one of the outer surfaces of the positive and negative terminals of the flat type gas depolarizable galvanic cells and a hydrophobic membrane of a certain value of Gurley number is employed in each cell in the battery pack.