PURPOSE: To facilitate the production of the title structure of a high resin content by using a resin of a small diameter, by immersing a fibrous structure in an aqueous suspension of a powdery thermosetting phenolic resin, adding a specified surfactant to the suspension, and removing the liquid from the fibrous structure after the agglomeration of the resin.

CONSTITUTION: A fibrous structure is immersed in an aqueous suspension of a powdery thermosetting phenolic resin of a diameter of 0.1-150μm, and a polyethylene glycol nonionic surfactant is added to this suspension. The liquid is removed from the fibrous structure after the powdery resin is agglomerated to obtain a composite structure comprising the fibrous structure and the powdery resin. According to the above process, the powdery resin 1 having a particle diameter small as compared with the network structure of the fiber 2 does not escape and separate from the composite structure to make the resin content uniform throughout the structure. Therefore a composite structure comprising a fibrous material and a resin material, having a high resin content and being capable of containing long fibers or continuous fibers can be safely and easily produced.