The general aspects of the data processing system, to get the response character of the ship statistically from the results of the seakeeping tests of actual ships, as well as of the model tests in irregular waves in the experimental tanks were discussed. A data processing system that is now under operation in the Ship Research Institute was introduced together with the descriptions on each elements of that system and the computing programs for the electronic computor to do the spectrum and correlogram analysis as a link of this system. An example of the application of this system to the actual ship performance test is reported, together with an attempt of the application of the results. Summary of the process to design the experiments, suitable for this kind of analysis, and some thoughts on the future development of this system were also mentioned.