PURPOSE: To obtain the steel plate having the necessary mechanical property and of the quality uniform over the whole length by adjusting the steel plate speed so that the steel plate becomes of the aiming temp. for cooling completion based on the detecting temp. of the steel plate at the inlet side of the cooling device.

CONSTITUTION: The conditions of a cooling start temp., cooling finish aiming temp., cooling speed, etc. are first set to a control computer 19. The control computer 19 the operates the water density, cooling start temp. pattern, the length of cooling zone and steel plate speed based on the conditions and outputs an operation signal to a cooling device 5 and roller table 11. It then finds the difference in the cooling start temp. based on the cooling start temp. detected at the inlet side of the cooling device 5 and operates the changing quantity of the steel plate speed. The arithmetic value is then outputted from the control calculator 19 to the driving motors 8, 12 of the roller and the cooling completion temp. of the steel plate S is controlled.