To provide a method of heating an immersion nozzle by which when the immersion nozzle for pouring molten steel for high cleanliness steel is preheated, temperature of the whole immersion nozzle is uniformly raised according to a prescribed temperature-raising profile and the erosion of the immersion nozzle at the casting time is prevented by preventing decarburization at the preheating time and thus, the high quality of the high cleanliness steel can be produced.

The method of heating the immersion nozzle is provided in which a flame-shielding plate 6 having the shape satisfying both expressions of W≥1.1×Wo, H≥1.1×Ho and either one expression of W≤2.5×Wo and H≤2.5×Ho, is set on and cover 100% or more of the projecting surface horizontally extended in the radius direction of the outer shape of a spouting hole 1a between the spouting hole 1a in the immersion nozzle 1 and a heating burner 5a disposed facing on the circumference to this spouting hole 1a , and this immersion nozzle is heated. Wherein, W: the width of the flame-shielding plate, Wo: the width of the spouting hole in the immersion nozzle, H: the height of the flame-shielding plate and Ho: the height of the spouting hole in the immersion nozzle.