A partition board that is arranged between two electrical storage elements that are arranged adjacent to each other in a predetermined direction (X direction) includes a guide portion, a first pin and a second pin. The guide portion is used to cause the partition board to move in the predetermined direction when each electrical storage element is arranged onto the partition board. The first pin protrudes in the predetermined direction, and is used to position the partition board in the predetermined direction. The second pin is provided at a location different in a top to bottom direction of the partition board from a location at which the first pin is provided, and protrudes in the same direction as the direction in which the first pin protrudes.