In this paper, wave drifting speed of a floating body is discussed.Measurements of wave drifting speed were conducted on both two-dimensional floating body and three-dimensional floating body. Then, the theoretical calculation method of wave drifting speed was derived from the analyses of measurement results. The mechanism of wave drifting speed varies with wavelength. In the range of short wavelength, wave drift force due to reflection waves drifts the floating body; therefore the drifting speed is decided by the equilibrium of wave drift force and fluid drag, and it is proportional to the wave sloop. In the range of long wavelength, on the other hand, wave drift force hardly acts on the floating body, because wave almost transmits the floating body; therefore the drifting speed is decided by the wave-current speed and it is proportional to the square of the wave sloop. Taking these wave drifting mechanisms into consideration, an estimation method of wave drifting speed, which covers entire wave range, is proposed.