An immersion nozzle comprising: a nozzle body composed of a refractory material and formed with an inner bore extending in a vertical direction; a flange composed of a flat plate-shaped refractory material, and joined to an outer periphery of an upper end of the nozzle body directly or through an adhesive, in a posture where it protrudes in a horizontal direction while surrounding the outer periphery of the upper end of the nozzle body; and a metal casing attached to surround an outer periphery of the flange and an outer periphery of a part of the nozzle body located just below the flange, wherein respective upper edge faces of the nozzle body and the flange lie in a same horizontal plane, and wherein the immersion nozzle is configured to be slidably moved in the horizontal direction while a lower surface of the flange is supported by a supporting device, and installed in such a manner that both of the upper edge faces of the nozzle body and the flange come into press contact with a lower edge face of an upper nozzle member located just above the immersion nozzle, the immersion nozzle being characterized in that: the nozzle body is formed such that a region of an outer peripheral surface thereof located above a point of power of an upward supporting force from the supporting device extends vertically up to an upper edge of the nozzle body without any dimensional change with respect to an central axis of the inner bore, wherein the outer peripheral surface region is not joined to the metal casing; and a joint strength between the nozzle body and the flange is less than a bending strength of each of the nozzle body and the flange. a nozzle body composed of a refractory material and formed with an inner bore extending in a vertical direction; a flange composed of a flat plate-shaped refractory material, and joined to an outer periphery of an upper end of the nozzle body directly or through an adhesive, in a posture where it protrudes in a horizontal direction while surrounding the outer periphery of the upper end of the nozzle body; and a metal casing attached to surround an outer periphery of the flange and an outer periphery of a part of the nozzle body located just below the flange, wherein respective upper edge faces of the nozzle body and the flange lie in a same horizontal plane, and wherein the immersion nozzle is configured to be slidably moved in the horizontal direction while a lower surface of the flange is supported by a supporting device, and installed in such a manner that both of the upper edge faces of the nozzle body and the flange come into press contact with a lower edge face of an upper nozzle member located just above the immersion nozzle, the immersion nozzle being characterized in that: the nozzle body is formed such that a region of an outer peripheral surface thereof located above a point of power of an upward supporting force from the supporting device extends vertically up to an upper edge of the nozzle body without any dimensional change with respect to an central axis of the inner bore, wherein the outer peripheral surface region is not joined to the metal casing; and a joint strength between the nozzle body and the flange is less than a bending strength of each of the nozzle body and the flange. the nozzle body is formed such that a region of an outer peripheral surface thereof located above a point of power of an upward supporting force from the supporting device extends vertically up to an upper edge of the nozzle body without any dimensional change with respect to an central axis of the inner bore, wherein the outer peripheral surface region is not joined to the metal casing; and a joint strength between the nozzle body and the flange is less than a bending strength of each of the nozzle body and the flange.