Disclosed is an immersion nozzle, which comprises a vertically-extending pipe-shaped straight nozzle body 10 adapted to allow molten steel to pass downwardly from an inlet port 9 provided at an upper end thereof, and a pair of discharge portions each including a respective one of a pair of outlet ports 12 provided in a lower portion of the straight nozzle body 10 in a bilaterally symmetrical arrangement and adapted to discharge molten steel laterally from a lateral side of the straight nozzle body. Each of the discharge portions has an inner surface defining the outlet port 12 and extending parallel to an axis of the outlet port 12 to define a length of the discharge portion at 45 mm or more. A ratio of S1/S2 is in the range of 0.8 to 1.8, wherein S1 is a total transverse vertical cross-sectional area of the outlet ports, and S2 is a cross-sectional area of an inner hole of the straight nozzle body taken along a plane including a line connecting respective inwardmost and uppermost positions of the outlet ports and extends perpendicularly to an axis of the straight nozzle body. The axis of the outlet port extends laterally outwardly and downwardly at the following angle θt with respect to a horizontal direction: 0°≦θt≦20°. The immersion nozzle of the present invention can suppress deceleration of a molten steel flow discharged from the outlet port to obtain a flow speed in an intended direction over a maximized distance.