An inertial measurement system includes three acceleration sensors detecting along three orthogonal axes, a display having several display areas, and a processor programed to perform a process. The processor calculates frequencies and spectral intensities of vibrations based on detected time series accelerations by three acceleration sensors and obtains relationship values between the calculated frequencies and the calculated spectral intensities. The processor causes the display to successively display an N-th value, intermediate values, and an (N+1)-th value of the relationship values at one display area in time series.