The author once pointed out that the face-cavitation around 0. 7 R might occur at the lowest number of rotations in the four-bladed propeller with ogival section, and emphasized at the same time that the blade-section around 0. 7 R should be designed perfectly to be an aerofoil section. Afterwards, the erosion that grows on the face around 0. 8 R in five-bladed propeller has frequently become an issue for discussion. The author, however, is of the opinion this is chiefly because the danger-section around O. 7 R in four-bladed propeller has slipped nearby to 0. 8 R which holds an almost perfect ogival section in five-bladed propeller. In planning cavitation free propeller it is insufficient to consider only 0. 9 R or other specific sections ; the author is of the opinion that the growth of cavitation all over the propeller should further be studied. For this purpose, it is necessary to make the pressure distribution of wing section in each radius quite clear. The author has made a surveying experiment on the pressure distribution, of the blade sections of Troost's type propeller and Kármán-Trefftz profiles with circular arc camber line, and wishes to report on the result of his experimentations.