A secondary battery comprising: an electrode group; a battery can for accommodating the electrode group; a battery lid for sealing an upper opening of the battery can; an external terminal (8A, 8B) provided on an outer side of the battery lid; a connection terminal (12A, 12B) electrically connected to the external terminal (8A, 8B); and a collector plate (4A, 4B) provided on an inner side of the battery lid and electrically connected to the electrode group and also electrically connected to the connection terminal (12A, 12B), wherein the collector plate (4A, 4B) and the external terminal (8A, 8B) are caulked and thereby fixed to the battery lid by the connection terminal (12A, 12B), the connection terminal (12A, 12B) includes a caulking portion (16A, 16B), a pressure-contact portion (18A, 18B) provided by pressurizing a part of the caulking portion (16A, 16B) into a stepped state for forming by pressurization a contact surface between the collector plate (4A, 4B) and the external terminal (8A, 8B), a contact portion between the collector plate (4A, 4B) and the external terminal (8A, 8B), and an outer peripheral side wall of the caulking portion (16A, 16B) is welded at least along the pressure-contact portion (18A, 18B), wherein in a radial direction starting at the outer peripheral side wall a depth of the welding increases in a direction from the caulking portion (16A, 16B) toward the battery lid, and in an axial direction starting at the contact surface (162 A) a depth of the welding increases in a direction from the outer peripheral side wall toward a center line of the connection terminal (12A, 12B), characterized in that the outer peripheral side wall has an end portion on the contact portion side melted in the welding and solidified and has a non-melted portion not melted in the welding on a portion in an in the axial direction away from the contact portion. an electrode group; a battery can for accommodating the electrode group; a battery lid for sealing an upper opening of the battery can; an external terminal (8A, 8B) provided on an outer side of the battery lid; a connection terminal (12A, 12B) electrically connected to the external terminal (8A, 8B); and a collector plate (4A, 4B) provided on an inner side of the battery lid and electrically connected to the electrode group and also electrically connected to the connection terminal (12A, 12B), wherein the collector plate (4A, 4B) and the external terminal (8A, 8B) are caulked and thereby fixed to the battery lid by the connection terminal (12A, 12B), the connection terminal (12A, 12B) includes a caulking portion (16A, 16B), a pressure-contact portion (18A, 18B) provided by pressurizing a part of the caulking portion (16A, 16B) into a stepped state for forming by pressurization a contact surface between the collector plate (4A, 4B) and the external terminal (8A, 8B), a contact portion between the collector plate (4A, 4B) and the external terminal (8A, 8B), and an outer peripheral side wall of the caulking portion (16A, 16B) is welded at least along the pressure-contact portion (18A, 18B), wherein in a radial direction starting at the outer peripheral side wall a depth of the welding increases in a direction from the caulking portion (16A, 16B) toward the battery lid, and in an axial direction starting at the contact surface (162 A) a depth of the welding increases in a direction from the outer peripheral side wall toward a center line of the connection terminal (12A, 12B), characterized in that the outer peripheral side wall has an end portion on the contact portion side melted in the welding and solidified and has a non-melted portion not melted in the welding on a portion in an in the axial direction away from the contact portion.