A mounting structure is provided for vehicular electrical equipment to be mounted between a floor panel and a seat disposed on the floor panel. The floor panel is provided with a plurality of seat rails for mounting one or more seats such that a position thereof can be adjusted longitudinally. In this mounting structure, the battery pack or the fuel cell assembly is divided into a plurality of battery units or a plurality of fuel cell units. Each of the battery units or the fuel cell units is disposed between a pair of the seat rails.