A battery module, comprising: a cell assembly including a plurality of secondary batteries that respectively have a plurality of electrode leads and are arranged to be stacked in at least one direction; and a bus bar assembly including a plurality of bus bars configured to electrically connect the plurality of secondary batteries and having at least one perforation hole into which the electrode leads are inserted, and a bus bar frame configured so that the plurality of bus bars are mounted to an outer side surface thereof, wherein the bus bar frame includes: a bus bar fixing portion having an insert space elongated in the right and left direction so that a position of the bus bar in the right and left direction is freely set, the bus bar fixing portion being configured to fix a top end and a bottom end of the bus bar; and a bus bar open portion opened so that the perforation hole of the bus bar is exposed inwards as the position of the bus bar in the right and left direction is changed, and wherein the bus bar has a plate shape, and wherein a perforation hole perforated in the front and rear direction is formed in the plate shape of the bus bar, and wherein the bus bar fixing portion has an insert groove into which at least one of the top end and the bottom end of the bus bar is inserted, the insert groove having an upward or downward recess elongated in the right and left direction, and wherein a plurality of fixing protrusions protruding toward the bus bar are formed at predetermined intervals on an inner surface of the insert groove, and a fitting groove having an upward recess is formed at an end of the bus bar so that the fixing protrusion is inserted therein. a cell assembly including a plurality of secondary batteries that respectively have a plurality of electrode leads and are arranged to be stacked in at least one direction; and a bus bar assembly including a plurality of bus bars configured to electrically connect the plurality of secondary batteries and having at least one perforation hole into which the electrode leads are inserted, and a bus bar frame configured so that the plurality of bus bars are mounted to an outer side surface thereof, wherein the bus bar frame includes: a bus bar fixing portion having an insert space elongated in the right and left direction so that a position of the bus bar in the right and left direction is freely set, the bus bar fixing portion being configured to fix a top end and a bottom end of the bus bar; and a bus bar open portion opened so that the perforation hole of the bus bar is exposed inwards as the position of the bus bar in the right and left direction is changed, and wherein the bus bar has a plate shape, and wherein a perforation hole perforated in the front and rear direction is formed in the plate shape of the bus bar, and a bus bar fixing portion having an insert space elongated in the right and left direction so that a position of the bus bar in the right and left direction is freely set, the bus bar fixing portion being configured to fix a top end and a bottom end of the bus bar; and a bus bar open portion opened so that the perforation hole of the bus bar is exposed inwards as the position of the bus bar in the right and left direction is changed, and wherein the bus bar has a plate shape, and wherein a perforation hole perforated in the front and rear direction is formed in the plate shape of the bus bar, and wherein the bus bar fixing portion has an insert groove into which at least one of the top end and the bottom end of the bus bar is inserted, the insert groove having an upward or downward recess elongated in the right and left direction, and wherein a plurality of fixing protrusions protruding toward the bus bar are formed at predetermined intervals on an inner surface of the insert groove, and a fitting groove having an upward recess is formed at an end of the bus bar so that the fixing protrusion is inserted therein.