To provide a base having excellent surface smoothness and a processing for producing the same.

The base formed by coating both surfaces of raw paper with polyolefin resins consists of craft pulp composed of aspen at 30 to 80wt.% in the pulp constituting the raw paper. The base is formed by beating the craft paper consisting of the aspen in such a manner that its water retention value attains 150 to 180%. The process for producing the base is executed by pressing the web surface side corresponding to the surface coated with photographic emulsions of the raw paper to a drum drier cylinder 2 via a drier canvas 3 and drying the raw paper under conditions of the tensile force of the drier canvas 3 adjusted to 1.5 to 3kg/cm, more preferably 2 to 3kg/cm by adjusting a canvas tension adjusting roll 5.