PURPOSE: To provide a curing agent for a furan resin, exhibiting a suitable acidity and a sufficient solubility in water and a solvent and capable of being taken into a cured material by copolymerization with the resin after curing and consequently producing a uniform cured material free from a void or unevenness of cure.

CONSTITUTION: A furan resin is cured by a liquid curing agent for a furan resin, composed mainly of o-aminophenol sulfuric acid salt and the cured material is carbonized. Thereby, the objective glassy carbon material is obtained.