The invention relates to a device (1) for state monitoring in hydrostatic displacement units (2), in particular in axial piston machines (3) operated as a pump or as a motor. The device (1) comprises an acquisition unit (4) with a multiplicity of sensors (5) which are attached to the hydrostatic displacement unit (2) and serve to acquire monitoring data (6) and operating data (7), and an evaluating unit (8) which has a device (9) for analysing the monitoring data in the frequency range and a device (10) for analysing the monitoring data in the time range. A diagnostic unit (11) with an output unit (13) is connected to the evaluating unit (8).