A mosaic virus disease of ginger plant was investigated to determine its virus group on the basis of host range, physical and chemical properties, serological behavior and electron-microscopic morphology. The disease gave rise to yellowsih and dark-green mosaic on the leaves in the early stage and stunted all the leaves as well as rhizomes in the late stage. In the field about 43\% of the plants were observed to be diseased The disease was able to be artificially infected to the ginger plants by the sap and transmission as well as to 23 other species of plants which were known to be the CMV susceptible plants by the sap transmission; Chenopodium amaranticolar, Nicotiana tabaccum var. Havana, cow pea, cucumber, tomato,... etc. The dilution end point of the virus ranged $10^{-4}-10^{-5}$ and the thermal inactivation point $65-70^{circ}C$. Serological test showed a positive reaction by a CMV antiserum. An electron microscopy of the purified virus showed that the virus particles were spherical with a diameter of $28-32mmu$. Virus particles from the infected tissue were observed to be free or aggregated in the mesophyll tissue of artificially infected tobacco plant. The mosaic disease of ginger plants were conclusively suggested to the CMV group.