A structure for mounting a power supply apparatus on a vehicle includes a driver's seat and a passenger's seat installed within a vehicle compartment and aligned in the vehicle width direction, an instrument panel provided at the vehicle front inside the vehicle compartment and equipped with electronics, a battery pack assembly located between the driver's seat and the passenger's seat, and wire harnesses electrically connected to the battery pack assembly. The vehicle front side and the vehicle upper side of the wire harnesses face the battery pack assembly. With the above-described configuration, there is provided a structure for mounting a power supply apparatus on a vehicle where the electronics provided at the instrument panel are appropriately protected from an electromagnetic wave.