Destruction of marine ecology system induced by the bal last water discharged from ships is one of the most serious problem among the various ship associated environmental impacts. International Maritime Organization (IMO) has actively dealt with this problem for a long time and is going to start to activate very strong international treatment for preventing ocean from such serious environmental impact. Various technologies of ballast water treatment are now being developed all over the world. In this paper, recent trend of existing ballast water treatment technologies is investigated in detail. Furthermore, in order to apply electrolysis technology to ballast wale r treatment, its basic principle is reviewed theoretically and its feasibility is checked through some in-situ experiments. Quite good results are shown in the experiments enough to confirm its applicability in ballast water treatment.