Nylon-6/poly(ethylene terephthalate) (PET) ultra-multi-island sea-island conjugated melt-spun fibers are flow-drawn at a draw ratio of 174 with heating by CO2 laser irradiation. Continuous PET nanofibers that have a diameter of 39 nm could be obtained from the flow-drawn fiber with further drawing and removal of the sea component. In addition, the drawn fiber has a strength of 0.54 GPa. this result shows that a PET nanofiber having a strength almost equal to that of a conventional PET fiber can be obtained by the combination of conjugate-melt-spinning and laser-heated flow-drawing.