A multichamber pressure-increasing device is comprised of a plurality of chambers disposed in series one inside the other, wherein the innermost chamber is configured so as to place objects or samples therein to subject them to ultra-high pressures. An external hydraulic pump pumps fluid into the outermost chamber while a plurality of elemental hydraulic motor pump systems (EHMPS) are mounted in each chamber for increasing the pressure from one chamber to the next one disposed more to the interior of the device through an iterative process, each EHMPS consisting of two cylinder-piston assemblies operatively joined together in such a way that both pistons extend or retract simultaneously within their respective cylinders, the motor part driving the pump part as pressurized fluid admitted into the motor cylinder is subsequently discharged so fluid admitted into the pumping part cylinder is compressed therein and impelled at a higher pressure into the succeeding chamber.