PURPOSE: To prevent flaw on the inside surface of tube that is disadvantageous in respect of cost and productivity by rolling after spraying a lubricant solution of a specified concentration of water glass which is diluted with water in a specified ratio to the inside surface area of tube.

CONSTITUTION: A tube stock is rolled with an elongator. Then, water glass is diluted with water and, after spraying the lubricant solution of 10 to 75wt.% in the concentration of water glass from the nozzle at the tip of plug in the ratio of ≥20g/m2 to the inside surface of tube, a seamless tube is manufactured by rolling. The seamless tube is made of a high alloy steel. In this way, friction between the inside surface of the tube stock and a tool is decreased due to the effect of glass lubrication and shearing strain is reduced, so flaw on the inside surface of tube is reduced.