A rectangular secondary battery (1) includes a current interrupting portion (60) disposed in a current path between a collector plate (21) connected to a rolled electrode group (40) and an external terminal (61) disposed outside a battery container (2) and configured to interrupt the current path when an internal pressure of the battery container (2) is increased. The current interrupting portion (60) has a diaphragm (68) electrically connected to the external terminal (61) and deformed when the internal pressure of the battery container (2) is increased, a connection plate (24) connected to the diaphragm and disconnected from the diaphragm by the deformation of the diaphragm, and a connecting portion (23) connecting the connection plate and collector plate. A rigidity of the connecting portion (23) is lower than that of the collector plate (21).