PURPOSE: To obtain a resin impregnated base material for laminates having excellent heat resistance, etc., capable of packaging high-frequency calculating circuit, etc., by impregnating a glass base material with resin varnish obtained by mixing fluororesin dispersion with a silane coupling agent and drying the glass base material.

CONSTITUTION: A glass base material is impregnated with resin varnish prepared by blending (A) fluororesin dispersion (e.g. tetrafluoroethylene resin, etc.) with (B) a silane coupling agent [e.g. PhSi(OEt)3, etc.] and dried to give the aimed base resin. The blending ratio is preferably 5vol.% component B.