Mature embryo and developing seedings of Ginkgo biloba L. were embedded in a parablast and serially sectioned at 10㎛ to examine vascular differentiation and vascular transition. Procambium and protophloem formed a continuous system along the epicotylhypocotyl root axis and cotyledons in mature embryo, whereas protoxylem was differentiated discontinuously in the cotyledons and rarely in the upper hypocotyl. The traces of the first and second leaf primordia appeared almost at the same time oppositely to each other at the epicotyl and alternately with the cotyledon traces in the upper hypocotyl. The trace differentiated bidirectionally toward the epicotyl and root tips. The young root initially formed a diarch xylem. Then, as the traces of the first and second leaves were superimposed, the disrch xylem of the root was changed to triarch and tetrarch xylem, respectively. On the formation of primary vascular system of Ginkgo biloba, it is suggested that the primary phloem forms a continuous system throughout the seedling, whereas the primary xylem of the epicotyl is formed independently from that of the root-hypocotyl cotyledon system.