An ionic organic compound having a repeating unit of formula (I) can be synthesized easily from a readily available organic compound through a small number of reaction steps, can be produced without any purification technique such as chromatography, and can be used in a quite small amount for gelation of water or an ionic liquid without any other auxiliary solvent: [-(A-B-C)n-]•m(X)   (I) wherein A represents a group having a quaternary ammonium cation which is formed from a heterocyclic compound having at least one nitrogen atom; B represents a functional group, which may have a substituent, selected from amide, urea, urethane and peptide groups; C represents a divalent hydrocarbon group, which may have a substituent, capable of linking between A and B; X represents an anion; n represents the number of repeating units; m represents the total number of anions; and n and m are the same integer. A hydrogel using the compound is stable under acidic conditions, capable of setting a large amount of water with a small amount thereof, and capable of quickly recovering the original elastic modulus against structural disruption caused by mechanical distortion. The hydrogel is capable of directly gelling an ionic liquid without other solvent such as water when causing gelation. Further, the hydrogel is capable of easily dispersing carbon nanotubes in water whose load on the environment is low.