BATTERY AND BATTERY UNIT

A battery (3) includes a battery case (10) having an opening sealed with a sealing plate (13). The sealing plate (13) has a protrusion (13a) extending in a direction toward the outside of the battery case (10), and a ring-shaped insulator (32) is provided on an outer circumferential surface of the protrusion (13a). An inner circumferential portion (32e) of the insulator (32) is in contact with the outer circumferential surface (13b) of the protrusion (13a), and an outer circumferential portion (32d) of the insulator (32) is extended to be positioned on an opening end (10a) of the battery case (10).