In regard to the hull strength of cargo vessels, ore carriers and tankers, some measurements have been done during voyages, and the results of these theoretical. analysis have been published so far. On the other hand, while many large, fast container ships have been built recently, there still remain some problems to the hull strength in rough sea. In order to cralify these problems, we have measured the stresses of the hull of a container ship during one round voyage across the Pacific Ocean in winter. From these experiments, we obtained the following results. (1) From the estimation of the long term distribution of total longitudinal stress on upper deck, the maximum value is expected to be 10 kg/mm² in single amplitude for 20 years and consequently 16 kg/mm² with still water bending stress. (2) Horizontal stress on upper deck is comparatively small, however torsional stress reaches to 4080% of total longitudinal stress according to the sea states. (3) Longitudinal bending stresses separated from the measured stresses coincide with the theoretically calculated values of wave bending moment in head sea, but the formers are a little bigger than the latter in following sea. (4) The maximum wave bending moment in 20 years is expected to be 7 kg/mm² in single amplitude. This value is 70% of total longitudinal stress. (5) Maximum warping stress during this voyage was 2.2 kg/mm² and the maximum value in 20 years is expected to be 4.5 kg/mm² in single amplitude respectively.