From the viewpoints of energy saving，methane gas originated from biomass might be possibly utilized as a fuel for the automobile engine. In order to investigate its feasibility，an experiment was made on the characterization of the engine power using syntheseized two kinds of gases changing the purity of methane，80% and 60%，respectively which are both in the range of the low quality methane gas through fermentation. The results obtained show that it is feasible to work the automobile engine in the range of gas mixture over 60% methane and it is further necessary to develop an optimum device which increases a flow rate of the gas with an increase of the revolutional speed.