Effects of microwave heating on the content of phytic acid and phosphorus of soaked soybean were investigated. Phytic acid content of Danwon, Marly and Amsoy cultivars were found to be 19.19 ㎎, 18.38 ㎎, and 16.73 ㎎/g defatted soybean respectively. Inorganic phosphorus content of soybeans was significantly increased during microwave heating, while phytic acid and phytate phosphorus was gradually decreased. Microwave heating was more effective than autoclaving in reducing the phytate contents. It was also found that microwave heating to soybean of low moisture content was more effective than that of high moisture content for decreasing the phytic acid content. Soaking in 2.5% sodium chloride, 2% sodium bicarbonate, and mixed salt solution for 12 hrs was not effective on reducing the contents of phytic acid and phytate phosphorus, but microwave-heating after soaking in above solutions greatly decreased the contents of phytic acid and phytate phosphorus, whereas significantly increased inorganic phosphorus of soybeans.