A device for monitoring the lifetime of at least one hydraulic apparatus of an aircraft subjected to variations of hydraulic pressure (P) in flight, the device comprising an interface for receiving measurement data representative of the hydraulic pressure (P) of the apparatus as a function of flight time (t), characterized in that the apparatus comprises: a processing device comprising a means for detecting, based on the measurement data , a pressure (P) load (SOLL END ) of a damaging nature, defined by the fact that the pressure (P) comprises a pressure increase (ΔP AUG ), greater than a predetermined damage threshold (S ΔP ) greater than zero, followed by a pressure reduction (ΔP DIM ) greater than the predetermined damage threshold (S ΔP ), a means for calculating a pressure variation amplitude (DeltaP N ), equal to the maximum of the absolute value of the pressure increase (ΔP AUG ) of the pressure (P) load (SOLL END ) of a damaging nature and of the absolute value of the pressure reduction (ΔP DIM ) of the pressure (P) load (SOLL END ) of a damaging nature, a means for projecting the pressure variation amplitude (DeltaP N ) onto a prescribed decreasing curve (MOD) of damage model or a prescribed decreasing straight line (MOD) of damage model, giving a permissible number (N SOLL ) of pressure (P) loads of a damaging nature as a function of the pressure variation amplitude (DeltaP N ), for determining the permissible number (N SOLLN ) of pressure (P) loads of a damaging nature corresponding to the pressure variation amplitude (DeltaP N ) which has been calculated, a calculating means for calculating a potential damage ratio (R N ), equal to a determined number (NRef) of reference loads, divided by the permissible number (N SOLLN ) of pressure (P) loads of a damaging nature which has been calculated, a means for incrementing a cumulative (R NCUM ) potential ratio (R N ) counter by the potential damage ratio (R N ) which has been calculated. a processing device comprising a means for detecting, based on the measurement data , a pressure (P) load (SOLL END ) of a damaging nature, defined by the fact that the pressure (P) comprises a pressure increase (ΔP AUG ), greater than a predetermined damage threshold (S ΔP ) greater than zero, followed by a pressure reduction (ΔP DIM ) greater than the predetermined damage threshold (S ΔP ), a means for calculating a pressure variation amplitude (DeltaP N ), equal to the maximum of the absolute value of the pressure increase (ΔP AUG ) of the pressure (P) load (SOLL END ) of a damaging nature and of the absolute value of the pressure reduction (ΔP DIM ) of the pressure (P) load (SOLL END ) of a damaging nature, a means for projecting the pressure variation amplitude (DeltaP N ) onto a prescribed decreasing curve (MOD) of damage model or a prescribed decreasing straight line (MOD) of damage model, giving a permissible number (N SOLL ) of pressure (P) loads of a damaging nature as a function of the pressure variation amplitude (DeltaP N ), for determining the permissible number (N SOLLN ) of pressure (P) loads of a damaging nature corresponding to the pressure variation amplitude (DeltaP N ) which has been calculated, a calculating means for calculating a potential damage ratio (R N ), equal to a determined number (NRef) of reference loads, divided by the permissible number (N SOLLN ) of pressure (P) loads of a damaging nature which has been calculated, a means for incrementing a cumulative (R NCUM ) potential ratio (R N ) counter by the potential damage ratio (R N ) which has been calculated. <EOS>