A method for manufacturing a seamless steel tube, wherein a tubing
material for the seamless steel tube is produced by a hot working process
from a material having less workability, such as a high Cr--high Ni--high
C alloy steel including Cr at a content not less than 15 weight % and Ni
at a content not less than 20 weight % or a ferritic stainless steel
including Cr at a content not less than 16 weight %, and then cold drawn
at a reduction rate of not less than 15% and further cold rolled after
applying an appropriate heat treatment, so that a round or an inner
grooved steel tube is obtained. It is preferable that the hot extrusion
process is employed for the hot working process and a cold Pilger mill is
employed for the cold rolling process. In the cold rolling process, the
crackings or damage resulting from the reduced toughness of the tubing
material as well as the breakage of a mandrel in producing the round or
the inner grooved tube can be suppressed.