A nozzle for continuous casting of clean steel is capable of preventing adhesion of Al.sub.2O.sub.3-based inclusions to a wall surface of the inner hole of the nozzle while fully achieving an effect of a swirl vane. The swirl vane prevents drift in molten steel passing through the inner hole. The swirl vane is disposed in the inner hole. A wall surface is at least partly formed as a tubular-shaped refractory layer and is prepared by controlling a weight ratio of CaO/MgO and an apparent porosity to have a thickness of 3 to 20 mm, so as to prevent adhesion of Al.sub.2O.sub.3-based inclusions to the wall surface and the swirl vane while effectively maintaining the anti-drift effect for long hours. Further, inert gas is injected into a molten steel flow between an upper nozzle and the swirl vane to facilitate surfacing of Al.sub.2O.sub.3-based inclusions in a mold and reduce Al.sub.2O.sub.3-based inclusions in molten steel so as to achieve stable casting operation and high-quality steel with high cleanness.