A battery module comprising: a battery cell stack in which a plurality of battery cells are stacked; a lower frame covering a bottom surface and both side surfaces of the battery cell stack; an upper frame covering an upper surface of the battery cell stack; characterized by a busbar frame formed on each of front and rear surfaces of the battery cell stack; and a connection unit that connects the bus bar frame, wherein the connection unit is formed of a flexible flat cable and is located between the upper frame and the battery cell stack, wherein the connection unit comprises: a connection body that is located on the upper side surface of the battery cell stack; a connecting cable that has a structure of being respectively bent and formed in the direction of the bus bar frame from both ends of the connection body, and a connection unit connector that is connected to the connecting cable and coupled to the busbar frame, wherein the connecting cable includes a first connecting cable formed in a downward direction; a second connecting cable that has a structure of being bent and formed in one direction among the stacking directions of the battery cell stack from the first connecting cable; and a third connecting cable that has a structure of being bent and formed in the other direction among the stacking directions of the battery cell stack from the second connecting cable. a battery cell stack in which a plurality of battery cells are stacked; a lower frame covering a bottom surface and both side surfaces of the battery cell stack; an upper frame covering an upper surface of the battery cell stack; characterized by a busbar frame formed on each of front and rear surfaces of the battery cell stack; and a connection unit that connects the bus bar frame, wherein the connection unit is formed of a flexible flat cable and is located between the upper frame and the battery cell stack, wherein the connection unit comprises: a connection body that is located on the upper side surface of the battery cell stack; a connecting cable that has a structure of being respectively bent and formed in the direction of the bus bar frame from both ends of the connection body, and a connection unit connector that is connected to the connecting cable and coupled to the busbar frame, wherein the connecting cable includes a first connecting cable formed in a downward direction; a second connecting cable that has a structure of being bent and formed in one direction among the stacking directions of the battery cell stack from the first connecting cable; and a third connecting cable that has a structure of being bent and formed in the other direction among the stacking directions of the battery cell stack from the second connecting cable. a connection body that is located on the upper side surface of the battery cell stack; a connecting cable that has a structure of being respectively bent and formed in the direction of the bus bar frame from both ends of the connection body, and a connection unit connector that is connected to the connecting cable and coupled to the busbar frame, wherein the connecting cable includes a first connecting cable formed in a downward direction; a second connecting cable that has a structure of being bent and formed in one direction among the stacking directions of the battery cell stack from the first connecting cable; and a third connecting cable that has a structure of being bent and formed in the other direction among the stacking directions of the battery cell stack from the second connecting cable.