Proposed is a method for manufacturing an ultrathin metal pipe using a cold drawing method, by which the manufacturable range of thin sides in metal pipes can be expanded drastically. In a diameter-expanding drawing method, an inlet-side solid die, the diameter of which increases, is constant, or decreases from the engaging inlet side to the finishing outlet side, and an outlet-side solid die, the diameter of which decreases at least near the engaging inlet, are arranged in opposition connected on the same pass line; a tapered plug, the diameter of which increases from the engaging inlet side toward the finishing outlet side, is floated over the pass line; a raw pipe between the solid dies and the plug is made thinner while the thickness mean diameter is increased in the region of the inlet-side solid die; and the outer diameter is reduced by pressure and the tapered plug is floated in the region of the outlet-side die. The method offers great economic advantages, since it is possible to manufacture ultrathin seamless metal pipes and long pipes, and since process rationalization can be realized in terms of yield and efficiency.