The above ground biomass of a secondary forest and Sugi（Cryptomeria japonica）plantation stand at Sanbe University Forest were measured in 2006. The above ground biomass of the secondary forest recovered by natural regeneration were 44.1, 42.0, 58.1t/ha on the lower, middle and upper part of slope in the１st experimental site, and 29.2, 16.3, 100.3t/ha on the lower, middle and upper part of slope in the２nd experimental site, respectively. Those of Sugi plantation stand were 123.0, 132.8, 97.5t/ha in the１st experimental site, 70.7, 54.3, 68.9t/ha in the２nd experimental site, respectively. The pioneer species by natural regeneration dominated on the lower part of slope and the tree species regenerated by stump sprouting occupied high proportion on the upper part of slope. The amount of standing crop in plantation plot was occupied by Sugi and depended simply on tree age. The other tree species remained little in Sugi plantation plot. The biomass of grasses and herbs contributed to the vegetation recovery in the lower part of slope right after clear cutting almost disappeared in both a secondary forest and Sugi plantation forest at more than２０years after cutting because of the decline of light intensity of forest floor.