1. A tire inspection device comprising: a generating means that generates an integer numeric filter by changing a decimally notated analyzing wavelet into an integer, the decimally notated analyzing wavelet correlating time, corresponding to a tire surface position, and frequency, wherein the decimally notated analyzing wavelet is based on a frequency representing a characteristic portion of a predetermined tire surface structure, a storage means for storing the integer numeric filter; a detection means disposed so as to detect a surface structure on an inside of a tire; a transformation means for wavelet transformation of a detection signal from the detection means using the integer numeric filter as an analyzing wavelet; and an output means for outputting, as characteristic information, the characteristic portion representing a transformation result of the transformation means.