An inspection apparatus for inspecting a subject (sample) (for example, performing identification or imaging of the subject) using an expansion coefficient with a relatively small amount of data. The inspection apparatus includes a transforming unit that performs a wavelet transform on a terahertz time waveform obtained using a terahertz wave detected by a detecting unit. In addition, the inspection apparatus includes a selecting unit that selects, from a first expansion coefficient in the wavelet transform, a second expansion coefficient stored in advance and included in the first expansion coefficient. Furthermore, the inspection apparatus includes a comparing unit for comparing a first value of the second expansion coefficient with a second value of the second expansion coefficient selected by the selecting unit.