The present invention relates to a battery module having a planar seating portion, and more particularly to a battery module having a planar seating portion including a plurality of battery cells, a frame unit having a rectangular structure in which an upper surface and a lower surface of the frame unit are open to the plurality of battery cells electrically; a first cover protecting one surface of the frame unit; a second cover protecting the other surface of the frame unit; two battery cells received in the frame unit; and a BMU electrically connected to the two battery cells, wherein the frame unit includes a frame body including a first frame and a second frame connected to each other in a state of being spaced apart from each other by a predetermined distance such that the two battery cells are horizontally received therein while facing each other, each of the first frame and the second frame having a quadrangular shape, and a seating portion located in the middle of the frame body such that the BMU is located between the two battery cells, an upper surface of the seating portion being flat, the seating portion protruding by a predetermined height.