The permeation of water and ions into bean seeds is essential for processing and cooking of beans. The permeability of cations, K, Na, Ca, and Mg ions, into soybean seed tissue, especially aleurone layer, during water uptake was investigated to characterize the ion permeation into soybeans. Aleurone layers and seed coats contained relatively high concentration of endogenous K and Ca ions, and endogenous Ca ion, respectively. The amounts of Ca ion entered seed coats and aleurone layers were greater than those of other ions, respectively. Ion contents per dried aleurone layer and dried seed coat were almost same from each other. The release of Ca and Mg ions toward the inside tissue from the aleurone layer was observed during water uptake. The cell wall column of aleurone layers adsorbed more K and Na ions than Ca and Mg ions. These results suggest that the Ca ion entered soybean seeds is actively transported from the seed coat to the embryo through the aleurone layer. The active migration of Ca to soybean embryos would be greatly usefull for producing foods enriched with Ca in processing and cooking of soybeans.