The present invention relates to a pouch type secondary cell with high water-resistance. The pouch type secondary cell comprises a positive electrode, a separation layer, and a negative electrode. Here, the sealing unit of the secondary cell includes steps so that the sealing unit has an outer side thinner than an inner side in thickness. The present invention is advantageous in that the manufacture process can be simplified, the water-resistance and sealing property of sealing portions can be further improved, and the manufacture costs can be reduced.