As shown in FIGS. 3 and 4, the average of the orientation angles of the primary grains 11, that is, the average orientation angle is over 0° and 30° or less. This brings various advantages as follows. First, since each primary grain 11 lies in a direction inclined from the thickness direction, the adhesion between the primary grains can be improved. As a result, the lithium ion conductivity between a certain primary grain 11 and each of other primary grains 11 adjacent to the primary grain 11 on both sides in the longitudinal direction can be improved, so that the rate characteristic can be improved. Secondly, the rate characteristic can be further improved. This is because, when lithium ions move in and out, the oriented positive electrode plate 12 expands and contracts smoothly since the oriented positive electrode plate 12 expands and contracts more in the thickness direction than in the plate face direction, as described above, and thus the lithium ions also move in and out smoothly.
