To remove scale, scraps of tube end or the like which are presented in the interior of a pierced material almost completely and to drastically restrain the generation of pock marks and pits.

Between a 1st piercer 1 and the 2nd piercer 2 on the manufacturing line using the tube making method with a Mannesmann plug mill, after executing internal descaling which is executed by jetting high-pressure water from the rear end side A of the pierced material M while making the pierced material M one or more revolutions, a lubricant is jetted from the front end side B of the pierced material M to the interior and, if necessary, the jetting pressure of the lubricant is lowered than the pressure of the high-pressure water which is jetted at the time of descaling.