PURPOSE: To improve the yield of a product by ameliorating a cooling device for a hot rolled plate provided with a duplex clad pipe laminar header and cooling the whole length and width of the hot rolled plate uniformly.

CONSTITUTION: The pipe laminar header consists of an inner pipe 4 and an outer pipe 3, a water feeding pipe 7 is communicated with the inner pipe 4 through a flow adjusting valve 9 and a control valve 8, and slits 6 are provided in the direction of plate width. On the outer periphery of the outer pipe 3, two kinds of nozzles 1, 2 different in diameter are arranged in one line in the direction of plate width for each diameter. Gears 5, an intermediate gear 10 and a motor 11 are provided so that nozzles are made coincide with the respective slits 6 in position by rotating the outer pipe 3. A gear 10a is a driven gear to rotate another header.