Abstract: A starting material to be extruded made of a high alloy comprising, in mass %, Cr: 20 to 30% and Ni: more than 22% and 60% or less is heated to a temperature predetermined according to the contents of Mo and W and is subjected to a hot-extrusion process, the heating temperature T (° C.) satisfying a relationship of Formula (1), (2), or (3), which is expressed in terms of the average cross-sectional area A (mm2) of the starting material to be extruded, the extrusion ratio EL (?), and the extrusion speed V (mm/s). As a result, a high-alloy seamless tube can be produced without generating cracking and/or seam flaws. When 0%?Mo+0.5W<4%: T?1343?0.001322×A?1.059×EL?0.129×V??(1) When 4%?Mo+0.5W<7%: T?1316?0.001322×A?1.059×EL?0.129×V??(2) When 7%?Mo+0.5W: T?1289?0.001322×A?1.059×EL?0.

Abstract: A starting material to be extruded made of a high alloy comprising, in mass %, Cr: 20 to 30% and Ni: more than 22% and 60% or less is heated to a temperature predetermined according to the contents of Mo and W and is subjected to a hot-extrusion process, the heating temperature T (° C.) satisfying a relationship of Formula (1), (2), or (3), which is expressed in terms of the average cross-sectional area A (mm2) of the starting material to be extruded, the extrusion ratio EL (?), and the extrusion speed V (mm/s). As a result, a high-alloy seamless tube can be produced without generating cracking and/or seam flaws. When 0%?Mo+0.5W<4%: T?1343?0.001322×A?1.059×EL?0.129×V??(1) When 4%?Mo+0.5W<7%: T?1316?0.001322×A?1.059×EL?0.129×V??(2) When 7%?Mo+0.5W: T?1289?0.001322×A?1.059×EL?0.