Although it is reported that comparable carbon and nitrogen is stored in abandoned bamboo forests with neighboring broadleaved forest and Japanese cedar forests, coarse woody debris has not been considered in the estimate in bamboo forests. This study was aimed to understand contribution of woody debris on carbon and nitrogen storage in an abandoned Moso bamboo forest. For this aim, we examined carbon and nitrogen storage in woody debris (standing and downed culms), soil organic matter (litter layer and mineral soil) and aboveground and belowground biomass of bamboo. This study was conducted in Kasuya research forest of Kyushu\ University. Three study plots were established along a slope to consider spatial variation in woody debris. Carbon storage in standing and downed culms, litter layer and mineral soil were 11.2,13.8,2.7 and 17.1 Mg C ha-1, respectively. Woody debris accounted for 30.9 % of aboveground biomass of bamboo. Culm density of standing dead culms was 18 % of living culm density. Nitrogen storage in standing and downed culms, litter layer and mineral soil were 49.1,136.4,85.8 and 1468.2 kg N ha-1, respectively. Woody debris accounted for 56 % of aboveground biomass of bamboo. These results suggest that woody debris can affect carbon and nitrogen storage considerably, and therefore it is very important to evaluate the storage in the dead culms in an abandoned Moso bamboo forest.