We investigated the amount of stemflow and its water chemistry of Japanese red cedar trees planted in the Sambe Forest, Shimane University. Stemflow properties were related to the several tree?size parameters, i.e., DBH, tree crown projection area, tree crown surface area, tree crown volume and plant biomass. Of tree?size parameters, crown surface area showed the highest correlation with the stemflow amount. The electric conductivity (EC) and pH values of the stemflow water were also related to tree?size. EC of stemflow water increased with tree diameter. On the other hand, pH of stemflow decreased with tree diameter. The stemflow chemistry of trees with thinner diameter reflected the condition of precipitation outside forest. This is due to the difference in the water volume, which passed through the crown of cedar trees. Crown of the thinner trees collected more water than that of the thicker trees.