1-Deoxynojirimycin(1-DNJ) was hardly detected by general UV detector. Therefore, in this study, we analyzed 1-DNJ, a effective functional material in which was contained the leaves of Cudrania tricuspidata and its tea by gas-chromatography. Synthesized a TMS derivative by attaching trimethylsilyl group to 1-DNJ, analyzed this by GC, and could detect a good peak. The leaves of Cudrania tricuspidata contains $1154.83{pm}56.67$ ug/g.d.w of 1-DNJ and tea of Cudrania tricuspidata leaves does $8.01{pm}0.61$ ug/g.d.w. This means the contents of 1-DNJ was nearly identical to each other. The larger size of the leaves had the more contents of 1-DNJ and the middle region of collection was the highest than any other collective regions of leaves.