NOVELTY - The element has an auxiliary unit (150) that is arranged so that an electrode case (120), an electrical power collector (140) provided with a connection board unit (142) joined to an edge portion of the electrode case, an outer-end surface (146) of an edge portion of electrode case, an outer side of board unit are enclosed. The auxiliary unit is provided with a protrusion portion (155) provided in a direction of the board unit at a protrusion form from a surface opposite to outer-end surface of board unit. The auxiliary unit protrudes in a direction of board unit.    USE - Electrical storage element such as lithium ion secondary battery mounted in motor vehicle.    ADVANTAGE - The auxiliary unit is provided with a protrusion portion provided in a direction of the connection board unit at a protrusion form from a surface opposite to the outer-end surface of connection board unit so that the electrode case and electrical power collector are joined using the auxiliary unit such that arrangement of tool for fixing the auxiliary unit to the connection board unit is eliminated in the case of the movement to the place where joining by ultrasonic welding is performed so as to suppress the movement of width direction of connection board unit of auxiliary unit and the shift to the direction of electrode case of auxiliary unit. Thus, the joining of electrode case and electrical power collector is performed efficiently for stabilization of position with respect to the connection board unit. Hence, the quality of electrical storage element is improved effectively while suppressing the generation of foreign materials such as micro metal portion.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for manufacturing electrical storage element.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the auxiliary unit.    Electrode case (120)    Electrical power collector (140)    Connection board unit (142)    Outer-end surface of edge portion of electrode case (146)    Auxiliary unit (150)    Protrusion portion (155)