This paper deals with prediction of cavitation noise of full scale ship's propeller from model experiment and its comparison with full scale measurements performed on two ships, a cargo liner and a training ship. It is proposed to estimate separately the tonal noise and the broadband noise because of their different mechanisms of noise generation. The acoustic-mechanical reciprocity principle is applied for estimating the tonal noise, and for the broadband noise a semi-empirical formula is applied for estimation in low frequencies. Full scale measurements on actual ship were arranged to acquire far-field noise and to eliminate extraneous noise reflected from sea surface. The comparison between predictions and full scale measurements has shown agreement amply proving that the proposed method of cavitation noise prediction is valid for practical purposes.