A booster device for a hydraulic circuit comprising a high-pressure circuit (12) and a low-pressure circuit (16) connected to a system generating the high pressure and to receivers, said booster device maintaining a minimum pressure in the low-pressure part, characterized in that it comprises a hydraulic motor (30) of which the inlet is connected to the high-pressure circuit (12) and the outlet to the low-pressure circuit (16), which drives a booster pump (20) sucking the fluid from a reservoir (24), in order to discharge it into this low-pressure circuit.