To understand the damage of the sugi bark borer,Semanotus japonicusLacordaire, to larger Japanese cedars,Cryptomeria japonicaD. Don., we inoculated living cedar trees of different sizes with hatched larvae. We also studied the oviposition preference of adult borers to logs of different sizes. Almost all larvae inoculated into larger trees were killed by resin flow between the outer and inner bark; however, in smaller trees, about half of the larvae survived. In the oviposition preference test, female adults tended to attack logs with larger diameters. This suggests that despite the high mortality of the young larvae in the larger cedar trees, adults prefer large diameter trees because the rougher trunk surface presents more suitable hiding and oviposition sites. Bark roughness was considered to determine the occurrence of damage from the sugi bark borer.