The present invention discloses a battery pack, which comprises a plurality of unit cells (1) each of which has two electrode terminals (2 and 3), and which are connected in series or in parallel by connecting an electrode terminal (2 or 3) of a unit cell (1) to an electrode terminal (3 or 2) of an adjacent unit cell (1), characterized in that, the electrode terminals (2 and 3) each is formed in a sheet shape, and the connection between the electrode terminals (2 and 3) is the binding of two sheets. According to the present invention, the battery pack has a low internal resistance, light weight, and reliable connection.