In a mounting structure for a vehicle battery box, a battery box is supported in a suspended manner between left and right rear side frames at the rear of a vehicle with first and second cross members that are installed between the left and right rear side frames. The first cross member is fixed at a substantially front end of a rear deformation zone that is set at the left and right rear side frames. High-voltage equipment is fixed between the first and second cross members on the top surface of the right rear side frame. The battery box is electrically connected to the high-voltage equipment with a connecting member.