Goal-Post Mast is usually equiped on board of large cargo ships. It is regarded as a rigid frame under space loading conditions. But the process of calculating the stresses produced by loading is very complicated by usual method of analysis such as strain energy method. The simple procedure of stress analysis is developed in this paper by using of generalized slope deflection formulae for space rigid frame proposed by author taking account of bending moments, twisting moments, axial forces and shearing forces acting on the extremities of members. Taking the slopes and deflections of nodsl points as the statically indeterminate quantities, the fundamental equations of equilibrium are easily solved by successive substitutions. This method shows simpler process to solve the problem than by the strain energy method. And author shows simple formulae of stresses. Numerical study are performed on the goal-post mast fitted to Japanese standard cargo ship of A-T type.