To provide a warm-forging treatment method which can show excellent lubricity in warm forging.

The method for forming a lubricating film 15 used in warm forging includes: conducting the steps of forming a chemical conversion film and forming the lubricant film; and thereby forming a phosphated chemical-conversion film 11 which contains zinc phosphate or a refractory metal and zinc phosphate, and lubricant films 12 and 13 which contain a non-electrolyte component, on the surface of a material 1 to be forged. In the step of forming the chemical conversion film, the phosphated chemical-conversion film 11 is formed on the surface of the material 1 to be forged by electrolysis treatment. In the step of forming the lubricating film, the material 1 to be forged which has the phosphated chemical-conversion film 11 formed thereon is immersed in a lubricant tank in which a lubricant is dissolved or dispersed in a solvent, and the lubricant films 12 and 13 are formed on the material 1. The lubricating film 15 to be used in warm forging is formed of the phosphated chemical-conversion film 11 and the inorganic lubricating film 12 and/or the organic lubricating film 13, and is formed so that the amount thereof exceeds 50 g/m2.