Leaves of26kinds of trees collected monthly are analysed to know the seasonal changes of constituents (H_2O,and,N,P_2_O5,K_2O) in it. Results are as follows : 1) Generally, We could not find the particular type of change in every kinds of trees.2) However, the remarkable difference of contents of ash and N between evergreen trees and deciduous trees ; and of ash between broad-leafed trees and needle-leafed trees.3) Contents of ash in the deciduous trees are increased with the maturing of leaves. 4) We could not see the inter-relations of each constituents, but can classify the type of change in each constituents in 3 or 4 types.