A plurality of electrical storage elements (11) are electrically connected to each other, and parts of the peripheral surfaces of the electrical storage elements (11) contained in concave surfaces (29) are joined to the concave surfaces (29) with double-sided adhesive tape (35), so that the electrical storage elements (11) can be firmly fixed to a holder (27), and heat can be efficiently transferred from the electrical storage elements (11) to the holder (27) through the double-sided adhesive tape (35).