To prevent molding powder from fixing to the surface of a member consisting of a molding space by a method wherein a layer made of chrominum nitride formed by an ion plating treatment is provided on a portion, which at least contacts with the molding powder, of a surface made of a metal mem ber consisting of the molding space of a pipe.

On a portion, which at least contacts with a molding powder A, of a surface made of a metal member consisting of the molding space 8 of a β-alumina pipe, a chromium nitride layer 13 formed by an ion plating treatment is provided. Concretely, the chromium nitride layer 13 is formed at a portion contacting with the molding powder A of the surface of a mandrel 3 and of a bottom punch 9. Thus, the fixing of the molding powder to the surface of the member consisting of the molding space can be suppressed, the cleaning interval of an isostatic press molding device can be prolonged, the running efficiency of the device is improved, the installation of a powder removing device becomes unnecessary and the production cost of the β-alumina pipe can be reduced.