This paper reports a highly controllable three-dimensional (3D) sheath flow device for fabrication of artificial capillary vessels. Three step sheath injection type 3D flow device which realizes wide core and sheath structure variations by simply flow rate control was applied to fabricate double-layer coaxial Core-Sheath microfibers applicable for long micro capillary vessels by aligning and cultivating vascular endothelial cells. As a result, about a 3-centimeter-long microfiber which has the vascular endothelial cells fused mutually in the center was successfully formed after three days culture.