TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The catalyst is zinc, gallium, cobalt, iron, chromium, tungsten, molybdenum, rare earth metals, and/or their compounds. The catalyst material has a metallosilicate support.Preferred Process: Before aromatization process, sulfide in the bio-gas is removed by physical and/or chemical operations, and carbon dioxide concentration contained in the bio-gas is adjusted to 0.01-10 volume%. The concentration of carbon dioxide is regulated by a physical operation such as physical absorption or membrane separation method, or by chemical operation such as carbon dioxide absorption method. Alternately, the concentration regulation of carbon dioxide is performed by carrying out mixed dilution of bio-gas with other raw material gas such as natural gas. EXAMPLE - Bio-gas generated by methane fermentation process of organic waste, was collected and circulated in a ferric oxide catalyst filled container. The raw bio-gas material contained 1000-1500 ppm of sulfide. Minor constituent gas such as sulfide was removed from the bio-gas. Then, the bio-gas composition contained (in volume% (vol%)) methane (63.8), carbon dioxide (36.4), oxygen (0.035), nitrogen (0.111), hydrogen (0.012), carbon monoxide (not detectable (ND) (less than 0.5 ppm)), hydrogen sulfide (ND, less than 1.25 ppm), methyl thiol (ND, less than 1.25 ppm), sulfur dioxide (ND, less than 0.2 ppm) and ammonia (ND, less than 0.5 ppm). Then, pure methane of 17.2 times more quantity was mixed to the gas. The concentration of carbon dioxide was reduced to 2.0 vol%. Catalytic reaction container was filled with catalyst which was supported by metallosilicate support which contained 6 weight% of molybdenum with ZSM-5 (zeolite support having micropore and channel of 5-8 Angstrom by porous support). The bio-gas was supplied to the container, at SV = 3000 ml/g.cat./h. Further, aromatization reaction was performed at an internal pressure of 3 atmosphere and at 720degreesC. The reaction results showed that after 100 minutes of reaction, the methane conversion was 7.7%, and reaction speed of hydrogen was 7673.4 n-mol/s/g-cat and of benzene was 1115.2 n-mol/s/g-cat, and after 440 minutes of reaction, the methane conversion was 7.2%, and reaction speed of hydrogen was 6696.3 n-mol/s/g-cat and of benzene was 1018.4 n-mol/s/g-cat. Thus, the method efficiently produced benzene (aromatic compound) and hydrogen, from the bio-gas.