Abstract: The present invention relates to an organic-transition metal complex which can safely and reversibly store hydrogen in a high capacity, and a process for preparing the same. In order to achieve the objects, the hydrogen storage material according to the invention comprises a complex generated by combination of an organic substance containing a hydroxyl (—OH) group(s) with a transition metal containing compound, which can more effectively store hydrogen with more than one transition metal being bonded per molecule. Examples of the organic substances containing hydroxyl (—OH) group(s) include alkyl derivatives such as ethylene glycol, trimethylene glycol and glycerol, and hydroxyl-containing aryl derivatives such as fluoroglucinol. As the transition metal, titanium (Ti), vanadium (V) and scandium (Sc), which can make Kubas binding, may be mentioned.