Water surface fluctuations in turbulent open-channel flows are analyzed by using wavelet transforms. The data analyzed in this paper are water surface profiles measured by a simultaneous image measurement of velocity vectors and the water depth. The continuous wavelet transform with the Mexican Hat wavelet is applied to the water surface fluctuations for detecting their characteristics. The advection velocity, spatial scale, frequency of the water surface fluctuations are successfully extracted through the transform and are discussed with respect to the Froude number dependence.