An object is to provide a process for providing hydrogen or heavy hydrogens conveniently without the necessity of large-scale equipment and a process capable of performing hydrogenation (protiation, deuteration or tritiation) reaction conveniently without the use of an expensive reagent and a special catalyst. The production process includes a process for producing hydrogen or heavy hydrogens, containing subjecting water or heavy water to mechanochemical reaction in the presence of a catalyst metal, and a process for producing a hydrogenated (protiated, deuterated or tritiated) organic compound, containing subjecting an organic compound and water or heavy water to mechanochemical reaction in the presence of a catalyst metal.