A battery module comprising: a first module and a second module, each including a cell stack having a plurality of battery cells stacked vertically in a direction parallel to an X-axis of a rectangular coordinate system, and a bus bar frame assembly configured to cover a front surface and a rear surface, each extending in parallel to an X-Z plane of the above coordinate system of the cell stack; and two pairs of foldable side plates including a first pair of side plates configured to cover and pressurize one side surface and the other side surface of the first module and a second pair of side plates configured to cover and pressurize one side surface and the other side surface of the second module and hinged to the first pair of side plates, each pair of side plates (210, 220) being provided such that their surfaces are parallel to a Y-Z plane in the above coordinate system, wherein the bus bar frame assembly includes: a front bus bar frame configured to cover a front surface of the cell stack; and a rear bus bar frame configured to cover a rear surface of the cell stack, characterized in that the front bus bar frame includes a pair of module terminals electrically connected to the cell stack, wherein, when the pair of foldable side plates (210, 220) are unfolded, the pair of module terminals provided to the first module and the pair of module terminals provided to the second module face each other, and in that the battery module further comprises: an upper housing and a lower housing coupled to pairs of foldable side plates (210, 220) to cover upper surfaces and lower surfaces of the first module and the second module in a state where the pair of foldable side plates (210, 220) are unfolded while maintaining pressurization to the first module and the second module. a first module and a second module, each including a cell stack having a plurality of battery cells stacked vertically in a direction parallel to an X-axis of a rectangular coordinate system, and a bus bar frame assembly configured to cover a front surface and a rear surface, each extending in parallel to an X-Z plane of the above coordinate system of the cell stack; and two pairs of foldable side plates including a first pair of side plates configured to cover and pressurize one side surface and the other side surface of the first module and a second pair of side plates configured to cover and pressurize one side surface and the other side surface of the second module and hinged to the first pair of side plates, each pair of side plates (210, 220) being provided such that their surfaces are parallel to a Y-Z plane in the above coordinate system, wherein the bus bar frame assembly includes: a front bus bar frame configured to cover a front surface of the cell stack; and a rear bus bar frame configured to cover a rear surface of the cell stack, characterized in that the front bus bar frame includes a pair of module terminals electrically connected to the cell stack, wherein, when the pair of foldable side plates (210, 220) are unfolded, the pair of module terminals provided to the first module and the pair of module terminals provided to the second module face each other, and in that the battery module further comprises: an upper housing and a lower housing coupled to pairs of foldable side plates (210, 220) to cover upper surfaces and lower surfaces of the first module and the second module in a state where the pair of foldable side plates (210, 220) are unfolded while maintaining pressurization to the first module and the second module. a front bus bar frame configured to cover a front surface of the cell stack; and a rear bus bar frame configured to cover a rear surface of the cell stack, characterized in that the front bus bar frame includes a pair of module terminals electrically connected to the cell stack, wherein, when the pair of foldable side plates (210, 220) are unfolded, the pair of module terminals provided to the first module and the pair of module terminals provided to the second module face each other, and in that the battery module further comprises: an upper housing and a lower housing coupled to pairs of foldable side plates (210, 220) to cover upper surfaces and lower surfaces of the first module and the second module in a state where the pair of foldable side plates (210, 220) are unfolded while maintaining pressurization to the first module and the second module.