A battery module comprising: a first and a second plurality of cylindrical battery cells, each battery cell having at least two electrode terminals having different polarities formed at one end portion of the battery cell; an upper case having a bottom portion, the upper case comprising a first accommodating portion where a space in which the first plurality of cylindrical battery cells are inserted and accommodated is formed, a first gas discharge path formed at the bottom portion of the upper case and adjacent to electrode terminals of the first plurality of battery cells, the first gas discharge path extending in front, back, left, and right directions to externally discharge a gas discharged from the first plurality of cylindrical battery cells and where an open portion exposed in a first direction is formed, and a first gas discharge hole opened such that the first gas discharge path is connected to the outside; a lower case having a top portion, combined to the bottom portion of the upper case, the lower case comprising a second accommodating portion where a space in which the second plurality of cylindrical battery cells are inserted and accommodated is formed, a second gas discharge path formed at the top portion of the lower case and adjacent to electrode terminals of the second plurality of battery cells, the second gas discharge path extending in the front, back, left, and right directions to externally discharge the gas discharged from the second plurality of cylindrical battery cells and where an open portion exposed in a second direction opposite to the first direction is formed, and a second gas discharge hole opened such that the second gas discharge path is connected to the outside; and a cover sheet disposed between the bottom portion of the upper case and the top portion of the lower case to cover the open portions of the first and the second gas discharge path; and a plurality of wire type bus bars configured to electrically contact and connect the electrode terminals of the first and the second plurality of cylindrical battery cells to each other. a first and a second plurality of cylindrical battery cells, each battery cell having at least two electrode terminals having different polarities formed at one end portion of the battery cell; an upper case having a bottom portion, the upper case comprising a first accommodating portion where a space in which the first plurality of cylindrical battery cells are inserted and accommodated is formed, a first gas discharge path formed at the bottom portion of the upper case and adjacent to electrode terminals of the first plurality of battery cells, the first gas discharge path extending in front, back, left, and right directions to externally discharge a gas discharged from the first plurality of cylindrical battery cells and where an open portion exposed in a first direction is formed, and a first gas discharge hole opened such that the first gas discharge path is connected to the outside; a lower case having a top portion, combined to the bottom portion of the upper case, the lower case comprising a second accommodating portion where a space in which the second plurality of cylindrical battery cells are inserted and accommodated is formed, a second gas discharge path formed at the top portion of the lower case and adjacent to electrode terminals of the second plurality of battery cells, the second gas discharge path extending in the front, back, left, and right directions to externally discharge the gas discharged from the second plurality of cylindrical battery cells and where an open portion exposed in a second direction opposite to the first direction is formed, and a second gas discharge hole opened such that the second gas discharge path is connected to the outside; and a cover sheet disposed between the bottom portion of the upper case and the top portion of the lower case to cover the open portions of the first and the second gas discharge path; and a plurality of wire type bus bars configured to electrically contact and connect the electrode terminals of the first and the second plurality of cylindrical battery cells to each other.