Disclosed herein is a power switching module for a battery module assembly constructed in a structure in which a plurality of rectangular battery modules, each having a plurality of battery cells or unit modules connected in series to each other, are stacked in the width direction (the longitudinal direction) and the height direction (the transverse direction) by at least twos such that the rectangular battery modules generally constitute a hexahedral structure (hexahedral stack), outer edges of the hexahedral stack are fixed by a frame member, and input and output terminals of the rectangular battery modules are oriented such that the input and output terminals of the rectangular battery modules are directed toward one surface (a) of the hexahedral stack, wherein the power switching module comprises an insulative substrate mounted to the surface (a) of the hexahedral stack in a coupling fashion, elements mounted on the insulative substrate for controlling voltage and current during the charge and discharge of the rectangular battery modules, and connection members mounted on the insulative substrate for interconnecting the control elements.