The experimental study has been carried out to investigate the self-excited shock wave oscillation in a transonic wind tunnel using a circular arc airfoil (chord length of 120 mm, thickness of 15%). Shock wave position of each side and wake position were simultaneously measured by using two line scan cameras (line scan frequency of 32 kHz). Shock wave and wake fluctuations are analyzed by the wavelet transform with Gabor wavelet. The results show that the phase difference between shock wave fluctuations of each side are almost 180 degrees, and the phase difference between shock wave and wake fluctuations was fixed in spite of the change of the frequency.