The present study reports the numerical investigation of the method for calculating the hydrodynamic load distributions on the blades of a screw propeller in non-uniform flow. The basic theory of the method was developed by Dr. Hanaoka, in which he used the new procedure of solving the integral equation of the lifting surface. The procedure is similar to Flax's method, but it is fairly simple and more economical for numerical calculation than Flax's. Following facts are revealed by the results of the numerical investigation. a) Numerical results about the characteristics of the unsteady effects and the three dimensional effects concerned, agree with the results by the other methods. b) According that the unsteadiness becomes stronger, the 2nd and 3rd terms of the Birnbaum series become larger though the 1st term becomes smaller. c) The 4 th term of the Birnbaum series is always small in all the region except near the tip, which shows that the Birnbaum series of 4 terms may give the satisfied solution in the practical sense. d) The load distributions near the tip and the root remain not to have the satisfied solution. Next the method is applied to the cases of the propellers operating in the actual wake and the variation of load distributions, thrust, bearing forces, etc. are presented. Comparisons between theoretical and experimental results on the thrust variations show satisfactory agreement. It is showed quantitatively that unsteady effects appear strongly in case of the propeller with large blade-area.