A monitoring device comprising: a process data acquisition unit configured to acquire process data indicating an operation condition of a machine having a rotating shaft; a shaft vibration value acquisition unit configured to acquire a measurement value of a shaft vibration value of the rotating shaft under the operation condition indicated by the process data; a shaft vibration calculation model creation unit configured to create a shaft vibration calculation model and to perform system identification of the shaft vibration calculation model by performing adjustment of a parameter of the shaft vibration calculation model under operation condition during test operation using the process data and the measurement value of the shaft vibration value; a shaft vibration analysis unit configured to perform a shaft vibration value interpolation process to calculate a shaft vibration value under various operation condition of a predetermined range using the shaft vibration calculation model after the system identification was performed; a determination model creation unit configured to create a determination model configured to determine a normal value of the shaft vibration value according to the operation condition indicated by the process data, on the basis of the process data, the measurement value of the shaft vibration value measured during an operation of the machine and the shaft vibration value calculated using the shaft vibration analysis unit; and a monitoring unit configured to evaluate the measurement value of the shaft vibration value on the basis of the process data, the measurement value of the shaft vibration value, and the normal value determined by the determination model. a process data acquisition unit configured to acquire process data indicating an operation condition of a machine having a rotating shaft; a shaft vibration value acquisition unit configured to acquire a measurement value of a shaft vibration value of the rotating shaft under the operation condition indicated by the process data; a shaft vibration calculation model creation unit configured to create a shaft vibration calculation model and to perform system identification of the shaft vibration calculation model by performing adjustment of a parameter of the shaft vibration calculation model under operation condition during test operation using the process data and the measurement value of the shaft vibration value; a shaft vibration analysis unit configured to perform a shaft vibration value interpolation process to calculate a shaft vibration value under various operation condition of a predetermined range using the shaft vibration calculation model after the system identification was performed; a determination model creation unit configured to create a determination model configured to determine a normal value of the shaft vibration value according to the operation condition indicated by the process data, on the basis of the process data, the measurement value of the shaft vibration value measured during an operation of the machine and the shaft vibration value calculated using the shaft vibration analysis unit; and a monitoring unit configured to evaluate the measurement value of the shaft vibration value on the basis of the process data, the measurement value of the shaft vibration value, and the normal value determined by the determination model.