The susceptibility of marine medaka, Oryzias dancena to fish pathogenic viruses (infectious pancreatic necrosis virus (IPNV), viral hemorrhagic septicemia virus (VHSV), hirame rhabdovirus (HIRRV), infectious hematopoietic necrosis virus (IHNV), and lymphocystis disease virus (LCDV)) was investigated. The cumulative mortalities of fish immersed with IPNV (experimental condition: 15℃ sea water (SW)), VHSV (15℃ SW), HIRRV (15℃ fresh water (FW)) were 30%, 40% and 60%, respectively. In the fish immersed with IPNV (15℃ FW, 18℃ FW and SW), VHSV (15℃ FW, 18℃ FW and SW), HIRRV (15℃ SW), IHNV (15℃ FW and SW), LCDV (15℃ FW and SW, 18℃ FW and SW), and mock-challenged group, mortality rate was less than 10%. IPNV, VHSV and HIRRV were re-isolated from the dead fish. These results suggest that marine medaka is susceptible to IPNV, VHSV and HIRRV, although their susceptibility depends on the environmental conditions.