Orthonormal wavelet expansion method is applied to an analysis of atmospheric turbulence data which shows more than two decades of the inertial subrange spectrum. The result of the orthonormal wavelet analysis of the turbulence data is discussed in comparison with those of an artificial random noise. The local wavelet spectra of turbulence show a characteristic structure, which is absent in the artificial random noise and is identified with the trace of the energy cascade process. The higher-order structure function of velocity, obtained by the wavelet analysis, shows the intermittent structure of the flow field.