A method for producing a piercing-rolling plug to be used for producing a seamless steel tube/pipe, characterized in that using an equipment system for producing the piercing-rolling plug which comprises: a shotblasting device for applying shotblasting on a surface of the plug, and an arc-spraying device for performing arc-spraying of iron wires on a shotblasted surface of a base metal of the plug, so as to form a film containing Fe oxide and Fe thereon, wherein the arc-spraying device includes plural spraying booths (11, 11A, 11B, 11C) each of which is used to separately form part of the film in turn in each of sections into which the surface of the base metal of the plug is divided along an axial direction of the plug; melting the iron wires by an arc, and spraying molten material thereof onto the surface of the base metal of the plug using an arc-spray gun (13, 13A, 13B, 13C) which is disposed in each arc-spraying booth (11, 11A, 11B, 11C); the arc-spraying is carried out while an intersection angle θ between the center line (Ac) of a spraying stream from the arc-spray gun (13, 13A, 13B, 13C) and the surface of the base metal of the plug is maintained in a range of 35 degrees to 90 degrees; the arc-spraying is performed in air; the plug has a bullet shape, and includes a body portion and a tip end portion; and the arc-spraying device includes, as the spraying booths (11, 11A, 11B, 11C), a first spraying booth (11, 11A, 11B, 11C) and a second spraying booth (11, 11A, 11B, 11C); and the film formation in a region of the body portion among the surface of the base metal of the plug is carried out by the first spraying booth (11, 11A, 11B, 11C) and the film formation in a region of the tip end portion among the surface of the base metal of the plug is carried out by the second spraying booth (11, 11A, 11B, 11C). a shotblasting device for applying shotblasting on a surface of the plug, and an arc-spraying device for performing arc-spraying of iron wires on a shotblasted surface of a base metal of the plug, so as to form a film containing Fe oxide and Fe thereon, wherein the arc-spraying device includes plural spraying booths (11, 11A, 11B, 11C) each of which is used to separately form part of the film in turn in each of sections into which the surface of the base metal of the plug is divided along an axial direction of the plug; melting the iron wires by an arc, and spraying molten material thereof onto the surface of the base metal of the plug using an arc-spray gun (13, 13A, 13B, 13C) which is disposed in each arc-spraying booth (11, 11A, 11B, 11C); the arc-spraying is carried out while an intersection angle θ between the center line (Ac) of a spraying stream from the arc-spray gun (13, 13A, 13B, 13C) and the surface of the base metal of the plug is maintained in a range of 35 degrees to 90 degrees; the arc-spraying is performed in air; the plug has a bullet shape, and includes a body portion and a tip end portion; and the arc-spraying device includes, as the spraying booths (11, 11A, 11B, 11C), a first spraying booth (11, 11A, 11B, 11C) and a second spraying booth (11, 11A, 11B, 11C); and the film formation in a region of the body portion among the surface of the base metal of the plug is carried out by the first spraying booth (11, 11A, 11B, 11C) and the film formation in a region of the tip end portion among the surface of the base metal of the plug is carried out by the second spraying booth (11, 11A, 11B, 11C).