PURPOSE: To enable a printed wiring board to be lessened in shrinkage caused by the effect of tension induced at the manufacture of prepreg and warpage and torsion caused by shrinkage difference by a method wherein the printed wiring board is formed of printed wiring board material of triaxially woven glass cloth.

CONSTITUTION: Prepreg is manufactured with glass cloth 3 where strands 2 formed of bundled filaments are made to intersect each other at an angle of 60 degrees. Then, double-sided copper plated boards 0.6mm and 1.0mm in thickness are formed of the prepreg concerned. In succession, a printed wiring board is formed of the double-sided copper plate board.