An object of the present invention is to provide a process for producing high-purity hydroxytriphenylenes in which not only inexpensive raw materials can be used but also no complicated steps of deprotection such as dealkylation, and reduction and the like are necessary, and which is thereby advantageous in industrial production. Also there is provided a novel crystal of 2,3,6,7,10,11-hexahydroxytriphenylene monohydrate, which has satisfactory thermal stability. The process for producing a compound represented by the general formula (2) is characterized by reacting a compound represented by the general formula (1) in the presence of a metal oxide comprising a metal selected from trivalent iron, pentavalent vanadium and hexavalent molybdenum and of a nonvolatile strong acid: wherein, Rs are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms.