Monochamus alternatus adults emerging from pine logs to which non-woven fabric strips with Beauveria bassiana were applied were reared individually under field or laboratory conditions, and their mortality was investigated. Under field conditions in 2001 and 2002, accumulated mortality on the 15th day after emergence was 95 to 99% of adults emerging from logs with strips, and 68 to 90% of adults emerging from logs with no strips. Under laboratory conditions in 2001 to 2003, the mortality was 84 to 97% for adults emerging from logs with strips and 22 to 30% for adults emerging from logs with no strips. Since the adults emerging from logs with strips died quickly under field conditions, their total area of maturation feeding within 30 days after emergence was 42-51% that of adults emerging from logs with no strips, and most females died before their ovaries matured. Even though adults emerged from logs with strips, B. bassiana was not detected in 34-43% of dead adults under field conditions and in 12-34% of dead adults under laboratory conditions. However, the death was suggested to be influenced by the application of B. bassiana.