PURPOSE: To easily control foaming magnification without using fluorocarbon gas said to be harmful by impregnating a glass fiber nonwoven fabric with air mixed resin paste and supplying the impregnated fabric into a mold to heat and cure the same while the expansion of air bubbles is adjusted.

CONSTITUTION: A phenol resin compound consisting of a phenol resin, aluminum hydroxide being a filler functioning as a foam control agent and a curing agent is charged in a mixer and mixed while compressed air is injected into the compound to prepare a kneaded compsn. containing fine air bubbles. This air mixed kneaded compsn. is rubbed against a glass fiber nonwoven fabric to be infiltrated therein and five impregnated nonwoven fabrics are superposed one upon another to be received in a mold and the mold is hermetically closed to be reduced in pressure. Next, the mold is heated to resin curing temp. to be held at that temp. After natural cooling, the mold is opened to demold a molded product to obtain homogeneous fiber reinforced phenol resin foam.