Abstract: A prismatic battery case (3) has a configuration wherein a rectangular shorter-side plate (3a) has a thickness (A) larger than a thickness (B) of a longer-side plate (3b). When the prismatic battery case (3) is manufactured, a battery case material (8) punched into a predetermined shape undergoes deep drawing to form a first intermediate cup element (1) having a substantially elliptic cross section; the first intermediate cup element (1) undergoes redrawing successively in a plural stages to form a second intermediate cup element (2) having a substantially elliptic cross section which is smaller in minor-axis-diameter to major-axis-diameter ratio; and the second intermediate cup element (2) undergoes DI processing to form the prismatic battery case (3) having a substantially rectangular cross section wherein the thickness (A) of the shorter-side plate (3a) is made larger than the thickness (B) of the longer-side plate (3b).