An electrochemical device which is free from deterioration of properties due to a process of joining a rigid case and a conductive lid is provided. A welded part PP of a conductive lid 12 and a welded frame member 11d are joined each other by laser welding. A weld bead for joining the welded part PP and the welded frame member 11d is not exposed to an internal space of a rigid package 10; therefore, fused material, the coagulum thereof, or the like created during laser welding are prevented from entering into the internal space of the rigid package 10.