A method for producing a seamless metallic tube by cold rolling with a cold pilger mill, comprising the steps of: when elongating a hollow shell in such a manner that an outside diameter thereof is reduced while reducing a wall thickness thereof, selectively used are a pair of rolls and a tapered mandrel bar according to outside diameters and wall thicknesses of the hollow shell and a rolled tube as a product, the rolls each having a tapered groove caliber which decreases gradually in diameter from an engaging entry side of roll toward a finishing exit side thereof, the tapered mandrel bar decreasing also gradually in diameter from an engaging entry side toward an finishing exit side; and, a reduction rate Rd of outside diameter is set to not more than one-half of a reduction rate Rt of wall thickness, wherein Rd = 1 - d / do × 100 % Rt = 1 - t / to × 100 % do: outside diameter of hollow shell d: finishing outside diameter to: wall thickness of hollow shell t: finishing wall thickness, the method being characterized in that: used is a hollow shell made by a hot reducing mill process with one of (a) or (b): (a) a stretch reducer under the condition that a reduction rate of outside diameter in the stretch reducer is not more than 77%; (b) a sizer under the condition that a reduction rate of outside diameter in the sizer is not more than 33%. when elongating a hollow shell in such a manner that an outside diameter thereof is reduced while reducing a wall thickness thereof, selectively used are a pair of rolls and a tapered mandrel bar according to outside diameters and wall thicknesses of the hollow shell and a rolled tube as a product, the rolls each having a tapered groove caliber which decreases gradually in diameter from an engaging entry side of roll toward a finishing exit side thereof, the tapered mandrel bar decreasing also gradually in diameter from an engaging entry side toward an finishing exit side; and, a reduction rate Rd of outside diameter is set to not more than one-half of a reduction rate Rt of wall thickness, wherein Rd = 1 - d / do × 100 % Rt = 1 - t / to × 100 % do: outside diameter of hollow shell d: finishing outside diameter to: wall thickness of hollow shell t: finishing wall thickness, the method being characterized in that: used is a hollow shell made by a hot reducing mill process with one of (a) or (b): (a) a stretch reducer under the condition that a reduction rate of outside diameter in the stretch reducer is not more than 77%; (b) a sizer under the condition that a reduction rate of outside diameter in the sizer is not more than 33%. do: outside diameter of hollow shell d: finishing outside diameter to: wall thickness of hollow shell t: finishing wall thickness, the method being characterized in that: used is a hollow shell made by a hot reducing mill process with one of (a) or (b): (a) a stretch reducer under the condition that a reduction rate of outside diameter in the stretch reducer is not more than 77%; (b) a sizer under the condition that a reduction rate of outside diameter in the sizer is not more than 33%. (a) or (b): (a) a stretch reducer under the condition that a reduction rate of outside diameter in the stretch reducer is not more than 77%; (b) a sizer under the condition that a reduction rate of outside diameter in the sizer is not more than 33%. (a) a stretch reducer under the condition that a reduction rate of outside diameter in the stretch reducer is not more than 77%; (b) a sizer under the condition that a reduction rate of outside diameter in the sizer is not more than 33%.