The present invention addresses the problem of providing a rectangular secondary battery having higher reliability by ensuring both mechanical strength and electrical characteristics between a metal body having a bus bar of an external terminal welded thereto, and a connection terminal bonded to the metal body. This rectangular secondary battery (100A) that solves the problem is characterized in that: external terminals (141, 151) of a positive electrode and a negative electrode are disposed on one surface of a rectangular battery container (101); a flat winding group is housed in the battery container; the external terminal (151) has a connection terminal (153) electrically connected to the flat winding group (170) by penetrating the battery container, and a metal body (152) bonded to the connection terminal; and a bonding section between the connection terminal and the metal body has a mechanically bonding section and a metallurgically bonding section.