With a method producing hydrogen by making iron or iron oxide contact water, water vapor, or a gas including water vapor, a hydrogen generating medium, which has a high hydrogen generation reaction rate and is resistant to a repetition of oxidation-reduction without degrading its activity, is provided by adding a different metal (such as Ti, Zr, V, Nb, Cr, Mo, Al, Ga, Mg, Sc, Ni, Cu, etc.) other than the iron to the iron or the iron oxide.