An underbody for a vehicle may arrange and couple a plurality of assemblies forming the underbody in a vertically laminating structure. The underbody includes a panel assembly configured to form a floor of a vehicle interior; an upper member assembly configured to be laminated on and coupled to an upper side of the panel assembly; and a lower member assembly configured to be laminated on and coupled to a lower side of the panel assembly and coupled to a side portion of the panel assembly and a side portion of the upper member assembly.