A battery includes: battery cell groups, each of which is obtained by connecting battery cells in series to each other; a battery casing storing the battery cells; a bus-bar connecting positive electrodes of the respective battery cell groups; a bus-bar connecting negative electrodes of the respective battery cell groups; and a first line connecting the positive electrode and the bus-bar, a second line connecting the negative electrode and the bus-bar, and a third line connecting the battery cells included in each of the battery cell groups. The first line and the second line are drawn to the outside of the battery casing and connected to the bus-bar, and the corresponding first and second lines are bent at the outside of the battery casing according to a position of the battery cell group in the battery casing and are connected to the bus-bar.