A battery pack, comprising: a pack body having a first main surface and a second main surface that are opposed to each other in a first axis direction, a first end surface and a second end surface that are opposed to each other in a second axis direction orthogonal to the first axis direction, and a first side surface and a second side surface that are opposed to each other in a third axis direction orthogonal to the first axis direction and the second axis direction; and a terminal unit including a plurality of terminals and the first end surface includes a plurality of terminal windows configured to expose the plurality of terminals along the third axis direction, wherein a first terminal window is configured to expose a positive terminal, a second terminal window is configured to expose a temperature detection terminal, a third terminal window is configured to expose a negative terminal and a fourth terminal window is configured to expose a part of a terminal of the plurality of terminals, wherein the third terminal window is arranged between the second terminal window and the fourth terminal window and closer to the fourth terminal window than to the second terminal window, wherein the first end surface includes a first concave portion provided close to the first side surface and a second concave portion provided close to the second side surface, and the first concave portion and the second concave portion are arranged on the first end surface and closer to the second main surface than the first main surface, wherein the first concave portion has a width dimension larger than that of the second concave portion in the third axis direction. a pack body having a first main surface and a second main surface that are opposed to each other in a first axis direction, a first end surface and a second end surface that are opposed to each other in a second axis direction orthogonal to the first axis direction, and a first side surface and a second side surface that are opposed to each other in a third axis direction orthogonal to the first axis direction and the second axis direction; and a terminal unit including a plurality of terminals and the first end surface includes a plurality of terminal windows configured to expose the plurality of terminals along the third axis direction, wherein a first terminal window is configured to expose a positive terminal, a second terminal window is configured to expose a temperature detection terminal, a third terminal window is configured to expose a negative terminal and a fourth terminal window is configured to expose a part of a terminal of the plurality of terminals, wherein the third terminal window is arranged between the second terminal window and the fourth terminal window and closer to the fourth terminal window than to the second terminal window, wherein the first end surface includes a first concave portion provided close to the first side surface and a second concave portion provided close to the second side surface, and the first concave portion and the second concave portion are arranged on the first end surface and closer to the second main surface than the first main surface, wherein the first concave portion has a width dimension larger than that of the second concave portion in the third axis direction.