Disclosed herein is a battery pack constructed such that a battery case, in which an electrode assembly is mounted, is made of a laminate sheet having high strength, side sealing parts of the battery case are formed in a specific shape, and a protection circuit module (PCM) is located in the inner space of at least one of the side sealing parts. The side sealing parts in themselves are used as a structure to decide the external shape of the battery pack, and, at the same time, are used as spaces for mounting the PCM therein. Consequently, it is possible to construct the battery pack without using additional pack sheathing members, to simplify the assembly process of the battery pack, and to manufacture the battery pack in a thinner and more compact structure with the reduced manufacturing costs. Furthermore, the PCM is located at either side of the battery cell while the PCM is spaced apart from electrode terminals. Consequently, the battery pack exhibits high safety against external impacts, such as dropping of the battery pack.