Helleborus net necrosis virus (HeNNV) is considered to be a causal agent of the black death disease of Helleborus spp,. There are no scientific reports showing successful transmission of the virus by mechanical and aphid inoculation, so far. In this study, it was shown that HeNNV was transmitted to Chenopodium quinoa and C. amaranticolor by mechanical inoculation using infected hellebore leaves, and was transmitted to hellebore seedlings by aphid (Myzus persicae) inoculation. Relatively high incidence of symptomless infection of the virus was found in a field survey at a park in Tokyo. Thirteen aphid species were recorded at the same field. Key Words : Helleborus net necrosis virus, carlavirus, black death, Helleborus spp.