PURPOSE: To simplify a stage and to improve the quality by using a mandrel bar for a core member and controlling both corners of a guide shoe and an interval between guide shoes while measuring the height of a spiral mark of a pipe after rolling.

CONSTITUTION: The height of a spiral mark of a pipe A' after rolling is detected by a spiral mark detecting device 60 in the lapse of times, and the detected result is inputted into an arithmetic and control part 50. The part 50 decides the variation of the height of the spiral mark, and the correlation between the guide shoe surface angle and the guide shoe interval η is required. In order to decrease the height of the spiral mark based on this correlation, how to change the guide shoe surface angle and the guide shoe interval η is required and the result is inputted into guide shoe setting and adjusting devices 41, 42. In addition, the devices 41, 42 control their attitudes and/or positions so that the guide shoe surface angle and the guide shoe interval η of the guide shoes 31, 32 correspond with the above-mentioned result.