This paper deals with the comparison between the calculated and measured Δ C_wA of the Waveless Stern, where Δ C_wA means the difference of the wave-making resistance between the models. without and with the stern bulb. The observed position of the stern flow separation (named X _s) is presented, together with the comparison between the observed and the calculated area of separation by Buri's method. The conclusions obtained are as follows. (1) The reduction factor β for the stern wave of the finer model C-101 falls by fitting the stern bulb, while for the fuller model C-201, it keeps same. (2) The area aft the observed X _s seems to be an actual separation area. The time -mean and the fluctuation are affected according to the phase (and amplitude) of the bow wave observed. at the vicinity of the separation point.