Disclosed herein are a frame member including an upper frame member having one major surface to which a protection circuit module (PCM) is mounted, and a lower frame member coupled with the upper frame member, the upper and lower frame members being provided at opposite major surfaces thereof with semi-cylindrical battery receiving parts corresponding to outer surfaces of the cylindrical unit cells mounted between the upper and lower frame members, a spacer provided at opposite major surfaces of a rectangular frame with pluralities of semi-cylindrical battery receiving parts corresponding to outer surfaces of the cylindrical batteries, the battery receiving parts being partially open such that the battery receiving parts communicate with neighboring battery receiving parts on the same plane, and a battery pack including the frame member and the spacer.