PURPOSE: To remarkably improve the accuracy of inside diameter in the hot rolling of a seamless steel tube.

CONSTITUTION: In the method for rolling the many kinds of sizes of seamless steel tubes by piercing and rolling a billet heated at a prescribed temp. in a heating furnace 1, a pierced and rolled tube stock is separately made into several kinds of intermediate tube stocks having different size of outside diameter by a 1st forming rolling for applying rolling-down of only an outside diameter in a sizer 4 and, after the rolling of the outside diameter and thickness is executed by rolling-down the inner and outer surfaces of the intermediate tube stock, a 2nd forming for applying the rolling-down of only the outside diameter is executed in an extractor 7. By deciding the size of outside diameter of the intermediate tube stocks which are separately manufactured in the sizer 4 so that the draft of outside diameter of the 2nd forming rolling is at most 10%, the seamless steel tube having a desired outside diameter and thickness is obtained.