The estimation of wave-induced response of a very large floating structure has been calculated by a coupled structure fluid interaction program. The evaluation of the calculated responses is mainly carried out on amplitude of motions, such as vertical displacements, accelerations. Although the nominal stress on the structure can be calculated by the program, it is very hard to obtain a detailed structural stress because the scale ratio of the detailed structure to whole floating structure is very large. This paper is concerned in the wave-induced stress response calculation procedure for the detailed vstructure on a very large floating structure. The calculation method consists of two steps. First step; Internal loads such as wave-induced bending moment and shear force and external load such as wave -induced water pressure, A_{ikc, s}(ω, χ;x, y ), are calculated by 3D coupled structure-fluid interaction program. Second step ; When these loads act in the same time on the structure, wave-induced stress for the detailed structure, σ_{ikc, s} (ω, χ;x, y) , can be calculated by using stress factor, k_j . σ_{i, s} (ω, χ;x, y) = ∑^N_j=1k_jA_{ijc, s} (ω, χ:x, y) To verify the procedure, we conduct a full scale measurement of 200×100m scale floating structure for 2 months. The estimated stress of detailed structure, for example stress around scallop at transverse bulkhead, shows very good agreement with measured stress.