To prevent the clogging of slit by forming a line crossing orthogonally perpendicular plane to the slit and the inner surface at the bottom of an immersion nozzle as a straight line or a curve bulged diagonally downward, interposing between the straight line rising with the inclination having a specific angle with the slit as the starting point and the inclined straight line having a specific angle or larger reaching the inner surface of the side wall of the same height as a spouting hole with the slit as the starting point.

The immersion nozzle is formed as a bottomed cylindrical state and a right and a left spouting holes 3, 4 are symmetrically positioned at the lower part of the side walls of the cylindrical shape and the slit 5 is arranged between the spouting holes. The line a-f is the straight line with the inclination having 30° to the horizontal line with the slit 5 as the starting point. The line a-g is the straight line with the inclination having ≥30° reaching the inner surface of the side walls of the same hight as the right and the left spouting holes 3, 4 with the slit 5 as the starting point. The line a-b is the line crossing the orthogonally perpendicular plane to the slit 5 and the inner surface of the bottom of the immersion nozzle. The line a-b is formed as the straight line or the curve bulged diagonally downward, by interposing between the line a-f and the line a-g.