NOVELTY - The power supply device has secondary battery cells (1) having an electrode terminal (lb) on upper surface of the cells and each having an angular outer shape. The separators are inserted in interface between adjacent battery cells for insulation in state where battery cells are stacked. A pair of end plates (3) is arranged at respective end surfaces of battery stack. A fastening element (4) fastens battery stack by fixing end plates together. A holder cover (25) covers upper surface of battery stack. The separator has engagement structure to be fixed with holder cover.    USE - Power supply device for electrical storage apparatus mounted on vehicle (all claimed) such as hybrid vehicle and electric vehicle, for use in household applications and factories.    ADVANTAGE - The holder cover covers upper surface of battery stack, so that the enlargement of a power supply device can be suppressed, the upper surface of the battery stack is covered reliably, and a waterproof structure can be achieved. The upper surface of a battery laminated body can be occluded in a waterproof state using a holder cover, and the waterproof structure using the existing substrate holder can be achieved in low cost, without adding the element for waterproof. Since the lower surface of a battery laminated body is covered with metal cooling plate, the disturbance and noise which comes from the lower surface side of a circuit board can be blocked more reliably. Since the shield board can be made into the product made from aluminum, the shield board can be comprised in low cost. The upper surface of a battery stack can be maintained in fixed height. Since the holder cover can hold the bus-bar which connects the electrode terminals, the holder cover can be fixed to the battery stack. Thus the fixation of the bus-bar of a secondary battery cell can be performed simultaneously, and can improve workability at the time of an assembly can be improved.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view illustrating assembled battery of the power supply device.    Secondary battery cells (1)    Electrode terminal (1b)    End plates (3)    Fastening element (4)    Holder cover (25)