An assembled battery comprises an assembled battery body and a top covering part. The assembled battery body is provided with a first main surface and a second main surface which are arranged opposite along a first axis direction, a first end surface and a second end surface which are arranged opposite along a second axis direction perpendicular to the first axis direction, and a first side surface and a second side surface which are arranged opposite along a third axis direction perpendicular to the first axis direction and the second axis direction. The top covering part is connected to the first end surface and comprises a plurality of square terminal windows, so that the plurality of terminals can be exposed outside. The terminal window arranged along the second axis direction at farthest side of the terminal windows is provided with a corner part. The corner part is formed in a curvature radius larger than those of other corner parts of the terminal windows.