The present invention relates to a battery module case, and more particularly, to a battery module case in which sub-battery modules are slidably mounted in a vertical or horizontal direction, wherein each sub-battery module comprises one or more battery cells, electrode tabs extending in one direction from the respective battery cells, and a pouched type case consisting of aluminum laminate sheets for covering the surfaces of the battery cells, except for the surfaces on which the electrode tabs are formed. The battery module case of the present invention is formed into an assembly type structure to be coupled to the outer surfaces of the sub-battery modules, wherein the outer surfaces include surfaces on which the electrode tabs are formed. At least two or more sub-battery modules are stacked and arranged in parallel, such that the surfaces on which the electrode tabs are formed are aligned in the same direction.