A battery module, comprising: a plurality of battery cells stacked one another and respectively having electrode leads protruding in the front and rear directions of the battery module; and a bus bar unit configured to connect the electrode leads of the plurality of battery cells, the bus bar unit includes: - a first bus bar frame mounted in front of the plurality of battery cells; - a first bus bar coupled to the first bus bar frame and connected to the electrode leads of the plurality of battery cells, which protrude to the front; - a second bus bar frame mounted behind the plurality of battery cells; - a second bus bar coupled to the second bus bar frame and connected to the electrode leads of the plurality of battery cells, which protrude to the rear; and - a sensing bus bar configured to electrically connect the second bus bar and the first bus bar and mounted to the first bus bar and the second bus bar, the sensing bus bar includes an elastic bending portion which is elastically bendable in the front and rear directions of the plurality of battery cells, wherein any one of the first bus bar frame and the second bus bar frame is mounted to the plurality of battery cells, the other one of the first bus bar frame and the second bus bar frame is configured to be slidably mounted in the front and rear directions of the plurality of battery cells. a plurality of battery cells stacked one another and respectively having electrode leads protruding in the front and rear directions of the battery module; and a bus bar unit configured to connect the electrode leads of the plurality of battery cells, the bus bar unit includes: - a first bus bar frame mounted in front of the plurality of battery cells; - a first bus bar coupled to the first bus bar frame and connected to the electrode leads of the plurality of battery cells, which protrude to the front; - a second bus bar frame mounted behind the plurality of battery cells; - a second bus bar coupled to the second bus bar frame and connected to the electrode leads of the plurality of battery cells, which protrude to the rear; and - a sensing bus bar configured to electrically connect the second bus bar and the first bus bar and mounted to the first bus bar and the second bus bar, the sensing bus bar includes an elastic bending portion which is elastically bendable in the front and rear directions of the plurality of battery cells, wherein any one of the first bus bar frame and the second bus bar frame is mounted to the plurality of battery cells, the other one of the first bus bar frame and the second bus bar frame is configured to be slidably mounted in the front and rear directions of the plurality of battery cells. - a first bus bar frame mounted in front of the plurality of battery cells; - a first bus bar coupled to the first bus bar frame and connected to the electrode leads of the plurality of battery cells, which protrude to the front; - a second bus bar frame mounted behind the plurality of battery cells; - a second bus bar coupled to the second bus bar frame and connected to the electrode leads of the plurality of battery cells, which protrude to the rear; and - a sensing bus bar configured to electrically connect the second bus bar and the first bus bar and mounted to the first bus bar and the second bus bar, the sensing bus bar includes an elastic bending portion which is elastically bendable in the front and rear directions of the plurality of battery cells, wherein any one of the first bus bar frame and the second bus bar frame is mounted to the plurality of battery cells, the other one of the first bus bar frame and the second bus bar frame is configured to be slidably mounted in the front and rear directions of the plurality of battery cells.