This article deals with the realistic and effective use of biomass mainly as an energy supply, since the fuel production from crops and other biomass resources has attracted much attention in the world. Several concrete examples of the evaluation of biomass utilization were exhibited from two different standpoints. One was “qualitative” evaluation, which includes the ratio of input/output energy, a new index of CO2 emission reduction, the comparison of the electricity generation density using solar energy, and the energy efficiency of cars with different source of power. The other was “quantitative” evaluation, which means the amount and distribution of readily-utilizable biomass resources and a comparison between the supply and demand of these resources. In conclusion, it was emphasized that the priority of biomass use should be as follows according to its economical value: human food is greater than animal feed, which is greater than industrial material, which is greater than fuel (energy). Thus, the cascade-type biomass utilization system should be sought; in addition, biomasses should be used as a local energy source, not as an alternative to petroleum.