To obtain a glass fiber nonwoven fabric for a printed circuit board having little deformation and extremely high accuracy by laminating each of the warp and weft at a constant pitch so as to mutually cross, bonding the crossing points, and coating a fixing agent insoluble in a matrix resin varnish at the surroundings thereof.

A warp 2 comprising glass fiber drawn out from creels 1 and arranged at a constant pitch is successively sent out on a cylinder surface and a weft drawn out from weft bobbins 3 on a bobbin carrier 4 arranged at the neighbor of the cylinder surface and coated with a binder by passing the weft through a dipping vessel is wound on the warp at the constant pitch in the nearly 90° direction to the warp direction to provide a laminate of the warp and the weft. A fixing agent insoluble in a matrix varnish containing an adduct of an epoxyamine and an isocyanate-based hardener is successively coated on the laminate of the warp and the weft in the warp direction by a constant width so as to form a narrow width. Thereafter, the movement of the warp on the cylinder surface is stopped, and the fixing agent is coated in the weft direction of the laminate. The coated laminate is heated and dried, and cut and opened at the center of the coated part of the fixing agent to form a flat board to provide the objective glass fiber nonwoven fabric.