PURPOSE: To prevent a steel pipe from bending during the cooling process by making a plate top chain or block chain travel with higher speed than a chain with dogs in the some direction along an ascending grade in a high temperature steel pipe cooling floor at the delivery side of a rolling mill.

CONSTITUTION: A steel pipe 1 to be cooled is mounted on the supply side of a plate top chain 7. The steel pipe 1 abuts against a roller 12 of a top chain 7 and stops according to the descending grade of the plate top chain 7. When the plate top chain 7 is travelled then in the ascending grade direction, the steel pipe 1 moves in the gradient direction and leaves from the roller 12 of the chain 2 with dogs while the steel pipe 1 rolls down to rollers 12 according to the grade. Since the chain 2 with dogs travels with lower speed than the plate top chain 7, the rotation of this steel pipe 1 is positively continued. Thus, the steel pipe being cooled and conveyed is prevented from bending.