A battery module (200, 201, 202, 203) comprising: a plurality of cylindrical battery cells including electrode terminals (111, 112) respectively formed at a top and a bottom of the plurality of cylindrical cells, the plurality of cylindrical battery cells being arranged in columns and rows in a horizontal direction; a module housing including an accommodation portion having a plurality of hollow structures to accommodate the plurality of cylindrical battery cells inserted into the module housing; and a bus bar configured to contact the electrode terminals (111, 112) of the plurality of cylindrical battery cells to electrically connect between the plurality of cylindrical battery cells, wherein the bus bar comprises: a main body portion that is positioned at a top or a bottom of the plurality of cylindrical battery cells and has a plate shape having upper and lower surfaces that are broader than a lateral surface of the main body portion in a horizontal direction; and a contact portion that is configured to electrically contact and be connected to an electrode terminal (111, 112) formed in one of the plurality of cylindrical battery cells, extends and protrudes from the main body portion in a horizontal direction, is stepped from the main body portion in a direction toward where the electrode terminal (111, 112) is positioned, characterized in that the contact portion includes a branched structure bifurcated in two directions with respect to a direction in which the contact portion extends and protrudes from the main body portion, wherein an embossed protrusion protruding toward where the electrode terminal (111, 112) is positioned is formed in the branched structure, and a contact area is set to allow a welding rod to establish electrical connection around the embossed protrusion in the branched structure. a plurality of cylindrical battery cells including electrode terminals (111, 112) respectively formed at a top and a bottom of the plurality of cylindrical cells, the plurality of cylindrical battery cells being arranged in columns and rows in a horizontal direction; a module housing including an accommodation portion having a plurality of hollow structures to accommodate the plurality of cylindrical battery cells inserted into the module housing; and a bus bar configured to contact the electrode terminals (111, 112) of the plurality of cylindrical battery cells to electrically connect between the plurality of cylindrical battery cells, wherein the bus bar comprises: a main body portion that is positioned at a top or a bottom of the plurality of cylindrical battery cells and has a plate shape having upper and lower surfaces that are broader than a lateral surface of the main body portion in a horizontal direction; and a contact portion that is configured to electrically contact and be connected to an electrode terminal (111, 112) formed in one of the plurality of cylindrical battery cells, extends and protrudes from the main body portion in a horizontal direction, is stepped from the main body portion in a direction toward where the electrode terminal (111, 112) is positioned, characterized in that the contact portion includes a branched structure bifurcated in two directions with respect to a direction in which the contact portion extends and protrudes from the main body portion, wherein an embossed protrusion protruding toward where the electrode terminal (111, 112) is positioned is formed in the branched structure, and a contact area is set to allow a welding rod to establish electrical connection around the embossed protrusion in the branched structure. a main body portion that is positioned at a top or a bottom of the plurality of cylindrical battery cells and has a plate shape having upper and lower surfaces that are broader than a lateral surface of the main body portion in a horizontal direction; and a contact portion that is configured to electrically contact and be connected to an electrode terminal (111, 112) formed in one of the plurality of cylindrical battery cells, extends and protrudes from the main body portion in a horizontal direction, is stepped from the main body portion in a direction toward where the electrode terminal (111, 112) is positioned, characterized in that the contact portion includes a branched structure bifurcated in two directions with respect to a direction in which the contact portion extends and protrudes from the main body portion, wherein an embossed protrusion protruding toward where the electrode terminal (111, 112) is positioned is formed in the branched structure, and a contact area is set to allow a welding rod to establish electrical connection around the embossed protrusion in the branched structure.