PURPOSE: To produce a pregreg free from measling an suitable as a material for printed bases, by impregnating a reinforcing sheet with a varnish prepared by adding dicyandiamide in an amount less than equivalent to epoxy resin to an epoxy resin component, and heating the impregnated sheet.

CONSTITUTION: In a process for producing a prepreg comprising impregnating a reinforcing sheet such as glass fiber cloth or paper with a varnish prepared by mixing (A) a resin component comprising (a) 40W95wt% polyepoxy compound and (b) 60W5wt% polyphenol with (B) a dicyandiamide curing agent, (C) a cure accelerator and (D) an organic solvent, heating the impregnated sheet and thereby removing the organic solvent and at the same time reacting compounds (a) and (b) with each other; said varnish comprises 100pts.wt. component A, 0.05W 3pts.wt. component C and 15W150pts.wt. solvent D and component B is used in such an amount that the ratio of the number of active hydrogens to the number R (calculated from the equation) of epoxy groups is 1.35W30.