Entomopathogenic fungi were isolated directly from a cadaver of adult M. saltuarius (infected with white fungi) supporting fungal sporulation, to develop biological control of pine wilt disease vector, M. saltuarius which was the most abundant in the middle to northern part of Korea and caused enormous damage to native pine tree in Korea, Japan and other regions of Asia. Pathogenicity of each fungus was tested using oak longicorn beetle, Moechotypa diphysis, as substitutive insect. As the result, only one of them showed pathogenic to adults of M. diphysis, with up to 100% mortality within 13 days of inoculation. Selected fungus was named as MsW1 and identified by Beauveria bassiana using microscopic examination, B. bassiana-specific PCR primers and genetic sequencing of the ITS region analysis. Pathogenicity test were conducted with various concentration of conidial suspensions of this isolate on M. saltuarius (3rd instar larvae and adults). Mortality rates varied from 57.1% to 100.0% and from 16.7% to 100.0% of M. saltuarius (3rd instar larvae and adults), respectively at 30 days. This is the first report of natural infection of M. saltuarius by B. bassiana.