A pressure monitoring apparatus for a membrane compressor, with at least one pressure transducer for recording the pressure within a certain volume, with at least one nonreturn valve and with at least one shutoff valve, for blocking of the nonreturn valve, the shutoff valve and the nonreturn valve each being located in a flow path through which a medium can flow between the volume and the pressure transducer. A pressure monitoring unit delivers exact measured values and which can be economically implemented is achieved by there being at least two nonreturn valves which are located anti-parallel in respective flow paths, the first nonreturn valve blocking in the flow direction from the volume to the pressure transducer and the second nonreturn valve blocking in the flow direction from the pressure transducer to the volume, and by there being at least two shutoff valves for blocking a respective flow path.