PURPOSE: To uniformize oil film on the surface of a rolling roll, and to prevent the local wear of the rolling roll, by spraying rolling mill oil from a slit nozzle against the surface of the rolling roll.

CONSTITUTION: A stationary outer tube 1, provided with a longitudinal slit 13 opening toward the rolling roll, is installed opposite to the rolling roll. An inner tube 2, in diameter smaller than that of the outer tube 1, provided with an ordinary flow slit 6 and an increased flow slit 7, and whose one end is connected to the oil supply source, is set inside the outer tube 1 so as to form a clearance between two tubes 1, 2. Next, an adjusting sleeve 3, provided with an inclined slit 8, is freely rotatably inserted into outside of the inner tube 2, in order to constitute the unit 10 which then sprays the rolling mill oil through the slit 13 against the rolling roll.