An inspection device includes a first data storage unit configured to store a first data which is time series according to a state of an inspection object, a second data generation unit configured to generate second data, which is a spectrogram including a first frequency component, a time component, and an amplitude component by performing short-time Fourier transform on the first data, a third data generation unit configured to generate third data including the first frequency component, a second frequency component, and the amplitude component by performing Fourier transform on time-amplitude data for each first frequency component in the second data, respectively, and a determination unit configured to determine the state of the inspection object based on the third data.