In the strength calculation of hull construction members, the mutual interference of respective members should naturally be taken into consideration. However, since such a calculation is very complicated and difficult, the strength calculations in the past have been limited to the extent of two dimensional ones. In view of this situation, this paper deals with three dimentional strength calculation which are considered to be generally practicable. By using Hardy Cross Method in the calculations of transverse members and normal functions in the calculations of longitudinal members, calculations of a sufficient accuracy have been attained with the effort of as small as 5 to 6 man days.