To provide a battery pack in which unit batteries are precisely positioned mutually at least in the X direction, and unit batteries that can constitute the battery pack in which the unit batteries are precisely positioned mutually at least in the X direction.

This battery pack 200 is composed by laminating the unit batteries 100 in a row mutually in the Y direction. Individual unit batteries 100 are provided with positioning parts (a first-1 positioning part 115 and a first-2 positioning part 116, a second-1 positioning part 117 and a second-1 positioning part 118) for positioning mutually at least in the X direction only at the center part of the X direction of a first outside wall part 110b and a second outside wall part 110c of the battery case 101 by being engaged with the positioning parts of adjacent unit batteries 100 (the first-1 positioning part 115 and the first-2 positioning part 116, and the second-1 positioning part 117 and the second-1 positioning part 118).