To provide a method for rolling seamless steel tubes by which a thin tube can be manufactured in the mandrel mill system by solving a perforation problem in the mandrel mill rolling, specifically, for example, to provide the method for rolling seamless steel tubes by which thin tubes having the following outside dia. ratios are obtained: the wall thickness/outside dia. ratio is two percent or less in common steel and the wall thickness/outside dia. ratio is four percent or less in martensitic stainless steel.
The oblique angle β of the cone type roll provided by pinching a pass line is 8° to 20° provisionally and the cross angle γ is 50 to 35° and a solid-core billet is perforated into a hollow raw tube and next, the hollow raw tube wherein a core bar is inserted is passed through rolling rolls of plural stands and the seamless steel tubes are rolled by pressing down the tube wall thickness so that the ratio (R1/DF) between a roll dia. DF of the rolling roll fillet of at least one stand and a curvature radius R1 of the rolling roll fillet is 0.275 or more.