Three major bays in Japan - Tokyo Bay, Ise Bay, Osaka Bay - are not only marine traffic congested areas but also rich fishing grounds, then many vessels come into conflict with many fishing boats. The purpose of this paper is to analyze background human factors on collision and aground accidents of fishing boats and recreational fishing boats in these three major bays. These background human factors are analyzed on the basis of the m-SHEL model. Using this analysis, it is found that these three major bays have background human factors which are significantly different from each other. This paper proposes useful analyze results to discuss for prevention marine accidents and marine safety management system.