Leaf biomass per unit of stem basal area at the crown base (ACB)is proportional to the leaf biomass based on the pipe model theory.  Recently a simple method for estimating leaf and branch biomass in Japanese cedar was developed.  In the method, the value of leaf and branch biomass per unit of ACB is required but there is not enough information.  In this study, we investigated leaf and branch biomass per unit of ACB from diverse climatic conditions and stand properties in 56 Japanese cedar plantation forests. In multiple regression model analysis, leaf biomass per unit of ACB was increasing with decreasing precipitation, increasing mean annual temperature, decreasing forest age, and increasing competition (Ry index).  Leaf biomass per unit of ACB was greater in warmer, water limited, and more crowded conditions. Branch biomass per unit of ACB was increasing with increasing forest age but the effects of climate conditions were not significant.  These results suggest that the factors that affects biomass per unit of ACB are different between leaf and branch and stand properties and climatic conditions should be considered for estimating leaf biomass in a Japanese cedar forest.