This experiment was made on the seasonal variation of mineral constituents of leaves of Sugi（Chryptomeria japonica D. Don), Hinoki(Chamaecyparis obtusa Sieb. et Zucc.) and Kuromatsu(Pinus Thunbergii Parl.), representative trees for afforestration in Japan. The author used the emission spectroscopy using a graphite electrod, and Cd as an internal standard element and has determined such elements as P, Mg, Al, Fe, Ca, Si, B, Mn and Cu. The calibration line of these elements are shown on the Figures 1～3. The analysis of N and K was done in the ordinary method. The method of sampling is as follows: Numbers of sample trees: three trees in each kind Dates when leaves were collected: May 16, July 5, August 24, Oct. 13 and Dec. 2, 1960. (Sampling intervals of 50 days). The differences of means based on season are tested by the analysis of variance. The significant differences at 5 % level are shown by the mark *, at 1 % level are shown by the mark ** in Tables 1, 2, 3. The seasonal variation of mineral constituents of leaves are summerized as follows and shown on Figures 4～6. (1)The contents of N, K and P of one year leaves seem to decrease from spring to autumn, whereas in two or three year old leaves such a tendency may not be recognizable. (2)The contents of Ca, Mg and Fe seem to increase from spring to autumn. (3)The contents of Mn, B, Si and Al in leaves of Kuromatsu seem to increase from spring to autumn, however, of Hinoki and Sugi may be constant. The amount of Cu seem to decrease. (4)It may be summarized that the ash ratios of leaves are connected with the date when leaves are collected and the age of leaves, since the ratios become higher from spring to autumn and as the year of leaves advances. The changes of ash ratio seem due to the deposition of the large quantity elements such as Ca, Si and Mg in leaves. In two or three year old leaves these elements are considered as surplus and released by falling of leaves.