The present paper was designed to investigate the effect of nitrogen, phosphorus and potassium on the histological differentiation of the young leaves of soybean (Glycinemax, M.). Observations were made on the numbers of lamina cells and lateral veins, width and thickeness of the lamina and vascularization of the midrib in the 5th leaf, and the differentiation of leaves at 42$mu$ from the apical tips of the shoot apecis. Samples were taken at the time when the 2nd leaf was completed. The experimental plots were divided into twelve parts. And the results obtained are as follows. 1) Nitrogen stimulated the differentiation of the leaf, the vascuralization of the midrib and increased the numbers of lamina cells and lateral veins. 2) Phosphorus promoted the differentiation of lamina at the first stage of soybean growth. It was more effective in the plots of excessive application than otherwise. It had a small effect on the differentiation of lateral veins. 3) Among the elements, a deficiency of postassium resulted in a reduced differentiation of the lamina potassium had no effect on the thickening growth of the lamina and the differentiation of the midrib. 4) It appeared that phosphorus might compensate for the negative effect of potassium in the potassium and phosphorus plots.