The present disclosure relates to a technique for manufacturing a humidifying membrane including a hydrophobic thin film-coating layer having a nano-sized crack morphology pattern on the surface of an aromatic hydrocarbon-based polymer ion exchange membrane and applying the membrane to a reverse electrodialysis process. The humidifying membrane including a hydrophobic thin film-coating layer having a nano-sized crack morphology pattern on the surface of an aromatic hydrocarbon-based polymer ion exchange membrane, manufactured according to the present disclosure, embodies a low bulk resistance of the ion exchange membrane and significantly improves ion selectivity, thereby overcoming the trade-off relationship between membrane resistance and ion selectivity, and thus may be commercially available as an anion and cation exchange membrane of a reverse electrodialysis device.