PROBLEM TO BE SOLVED: To provide a respiration monitor for correctly evaluating a disease state/condition of a subject and a respiratory dynamic state.SOLUTION: In a respiration monitor 1, a pressure sensor 10 detects a change (time series data on a respiratory pressure) of a respiratory pressure of a subject including a pressure by a flow rate of supply oxygen supplied to the subject from an oxygen concentrator to acquire a respiratory waveform. An offset estimation part 31 estimates an offset fluctuating with time and superimposed on the respiratory waveform when supplying oxygen by the oxygen concentrator on the basis of the respiratory waveform detected by the pressure sensor 10. An error compensation respiratory waveform arithmetic part 32 calculates an error compensation respiratory waveform that is the time series data on the respiratory pressure in which the offset superimposed on the respiratory waveform is compensated by use of the offset estimated by the offset estimation part 31. A respiratory dynamic state index value calculation part 33 calculates a respiratory dynamic state index value of the subject on the basis of the error compensation respiratory waveform calculated by the error compensation respiratory waveform arithmetic part 32.COPYRIGHT: (C)2015,JPO&INPIT