A method for producing an ultrathin-wall seamless metal tube, which employs a cold pilger mill of mechatronics drive type including a mechanism to give a feed and a turn angle to a tube material, utilizes a roll having a tapered groove whose diameter gradually increases or gradually decreases from an engaging entry side to a finishing exit side of a pair of rolls, and a tapered mandrel whose diameter similarly gradually increases from the engaging entry side to the finishing exit side to elongate the tube material by reducing a wall thickness while expanding a mid-wall diameter of the tube material. By giving amounts of a turn angle and/or a feed equivalent or nearly equivalent to the forward stroke to the tube material immediately before the start of a backward stroke, it is possible to achieve a further increase in the reduction-rate of rolling, a further reduction of wall thickness, and improvement of dimensional accuracy of the product.