PURPOSE: To control an interval between steel pipes accurately by operating a transport distance in a chasing control period by means of an interval between individual steel pipes at the entrance side of a group of detectors and at the exit side of them so as to instruct a speed change to a group of rolls in the front by means of the transport distance and the speed.

CONSTITUTION: Due to a set error of the skew angle θ of a skew turning roll 2 and a difference in slipping between a steel pipe and the skew turning roll 2 resulting from a difference in materials of skew turning roll and an abrasion of the skew turning rolls 2 and others, the transport speeds of steel pipes differ depending upon positions, but the steel pipes of the same length have repeatability in the same position, therefore by taking advantage of its feature an interval between a preceding steel pipe 10 and a following steel pipe 11 is controlled. Each passing speed of preceding steel pipe rear end and following steel pipe tip end between each detector is sought by plural detectors 22W28 detecting steel pipe ends and a chasing control starting point of the following steel pipe is operated by means of the sought speed distribution of the preceding steel pipe rear end and the following steel pipe tip end and others and thereby the rotating speed of the skew turning roll transporting the following steel pipe is controlled to change the interval between steel pipes into the expected value accurately.