PURPOSE: To obtain sufficient welding strength even in the state of solder welding when a lead terminal is laser-welded on the case of an electric double layer capacitor and the like.

CONSTITUTION: When a lead terminal 3, on the surface of which solder plating is provided, is going to be welded to the case 1a of an electric double layer capacitor and the like by laser welding, voids G are securely formed on the circumference of the welding part of the lead terminal 3, and the solder gas generated when a welding operation is conducted is dispersed through the voids G.