The invention relates to a device for monitoring the lifetime of at least one hydraulic apparatus of an aircraft that is subject to ventilations in hydraulic pressure during flight, comprising an interface for receiving measurement data which are representative of hydraulic pressure (P). The invention is characterised in that the device comprises a processing device, comprising a means for detecting a pressure (P) load (SOLLEND) of a damaging nature, which load is defined by the fact that the pressure (P) comprises a pressure increase (ΔPAUG) that is greater than a predetermined damage threshold (SΔP), followed by a pressure decrease (ΔPDIM) that is greater than the threshold (SΔP), a means for calculating a pressure variation magnitude that is equal to the maximum increase (ΔPAUG) and the maximum decrease (ΔPDIM), a means for projecting the magnitude onto a decreasing curve or straight line of a damage model in order to determine the permissible number of loads corresponding to the magnitude, a means for calculating a potential damage ratio that is equal to a number of reference loads divided by the permissible number, a means for increasing a count of accumulated ratios by said ratio.