In a battery including a battery cell formed in a flattened substantially parallelepiped shape and a terminal contacting section electrically connected to the battery cell, at one end in the longitudinal direction of a face of the battery opposing to the face on which the terminal contacting section is provided, a projecting portion which projects in the longitudinal direction of the face is provided. Meanwhile, another projecting portion which projects in the longitudinal direction of the face is provided at the other end. The projecting portions may have projecting lengths different from each other or may have projecting lengths and projecting thicknesses different from each other. A charging apparatus into which the battery is to be installed includes an accommodating section for the battery which in turn includes projection accommodating portions configured to individually accommodate the projecting portions.