The fall velocity of spherical particle is analyzed theoretically in taking account of the effects of fluid turbulence. The method of Fourier transformation is applied to the theory, from which the mean fall velocity of spheres is predicted in terms of the power spectral density function of vertical fluid oscillation. The method is applied to the suspended sand particles in a river, and the effect of turbulence on the fall velocity of sand particles is found to be negligible in natural geophysical flows as far as the nonlinear drag is concerned.