Highly pure metallic single-walled carbon nanotubes were continuously extracted from a mixture of semiconducting and metallic species using a nondestructive, scalable method. Two laminar streams were generated in an H-shaped microfluidic channel with two inlets and two outlets. The flow conditions were carefully controlled to minimize diffusive and convective transport across the boundary between the two flows. Dielectrophoretic force from the embedded electrode at the junction extracted metallic nanotubes from a stream of nanotube suspension toward the other stream of buffer solution without nanotubes. The highly pure metallic and enriched semiconducting nanotubes were obtained simultaneously at each outlet using this novel approach. Excellent selectivity was verified by electrical transport measurement, absorption, and Raman spectroscopic analysis.