Jatropha curcas has been expected as a biodiesel plant which can be grown in degraded lands. The structure of roots at the seedling stage, in particular cell wall modification in exodermis and endodermis, was microscopically observed. In addition, it was discussed if the first four peripheral roots that emerge from the base of the primary root (taproot) are lateral roots or adventitious roots. The primary root and the first-order lateral roots formed diarchy stele, in which two protoxylem poles present in primary xylem of root. Consequently, the first four peripheral roots cannot be lateral roots, but should be adventitious roots formed at the base of hypocotyl. In both the primary and first-order lateral roots, exodermis and endodermis formed highly lignified cell walls. Moreover, the exodermal and endodermal cell walls formed Casparian strips, which could be observed without special staining by fluorescent dye under ultraviolet microscopy. Such cell-wall modification in root exodermis and endodermis may play an important role for J. curcas under soil stresses in degraded lands.