TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The V group element contained in the base material is nitrogen and/or phosphorus.Preferred Property: The average particle diameter of the magnesium micro particles is 1-10 nm.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The V group element contained in the base material is nitrogen and/or phosphorus.Preferred Property: The average particle diameter of the magnesium micro particles is 1-10 nm.    TECHNOLOGY FOCUS - POLYMERS - Preferred Material: The polymer material has cyclic imide structure in at least one portion.Preferred Method: A polymer solution having carboxyl group in molecular structure is prepared. Magnesium carbonate is mixed with the polymer solution so that at least one portion of the carboxyl group reacts with magnesium atom, and salt having magnesium atom in polymer solution is formed. A polymer structure (P1) is obtained from the solution. A polymer structure (P2) is obtained using the polymer (P1), and used as carbon material precursor. A polymer solution is polyamic acid solution. The polymer structure (P2) has cyclic imide structure at least one portion. The temperature of heating decomposition process is baking temperature of 300-700degreesC. The resulting product is baked at temperature lower than the calcination temperature in predetermined atmosphere after baking process. EXAMPLE - Bis(4-amino phenol)ether (5 g) and dimethyl acetamide (120 ml) were stirred under nitrogen gas. Pyromellitic acid anhydride (5.45 g) was added to the mixed solution and stirred for 3 hours, and polyamic acid solution having carboxyl group in a molecular structure was produced. Magnesium carbonate particle having average particle diameter of 4 microns was mixed with polyamic acid solution in an amount of 30 volume%. The resulting mixture was stirred for 12 hours and the mixed magnesium carbonate particle was reacted with the carboxylic group in the polyamic acid, and salt having magnesium atom in polymer solution was formed. The produced magnesium-containing polyamic acid solution was applied to a slide glass dried and a nitrogen atmosphere for 1 hour, dried at room temperature under reduced pressure for 2 hours and heated at 100degreesC for 1 hour and film of pale yellow color was obtained. The film was heat-processed at 300degreesC for 1 hour and polyamide film with thickness of 100 microns was obtained. The film was baked from room temperature to 650degreesC and temperature increase rate of 3degreesC/minute in argon atmosphere, maintained at calcination temperature of 650degreesC for 3 hours and cooled to room temperature. The magnesium was changed to porous shape carbonization structure, which precipitated to fine particle. The obtained magnesium microparticles containing carbon material had fine holes inside the carbon base material and magnesium particles were distributed by the hole portion. Nitrogen of 3 atomic% was contained in the obtained carbon material. The obtained carbon material had hydrogen storage characteristic of 3.6 wt.%.