PURPOSE: To produce a seamless pipe in a high yield of products by coupling a continuous casting system and a seamless rolling stage rationally.

CONSTITUTION: The molten steel in a tundish 4 is charged into a continuous casting mold 3 and is cast continuously as an ingot 5. The continuously cast ingot 5 is curved and pulled upward and is further rolled in a horizontal state into a seamless steel pipe with a stretch reducer SR. The point where the molten steel remaining in the ingot 5 completes solidification in this method is so adjusted as to be higher than the level 1 of the molten steel in the mold 3. The thickness and temp. of the solidified shell of the ingot 5 are measured with plural measuring devices 7 for the solidified thickness of the ingot and measuring devices 8 for the temp. thereof in order to perform said adjustment and the heating and cooling devices 6 for the ingot 5 are adjusted with the measured signals thereof. Since the hollow continuously cast ingot consisting of the solidified shell wherein no residual molten steel exists is drawn with the stretch reducer SR, the seamless steel pipe is produced in an extremely high yield.