Recently, a requirement to fuel economy improvement is rising from the strong fear against the environment aggravation caused by CO2 that is discharged in the atmosphere. In such a situation, to pursue fuel economy, it pays attention to CVT and AMT as transmission form. However, the advantages and disadvantages about both of the transmission form weren't compared on the same condition in the past.In this paper, the shift schedule, the drive power characteristic, the body variation and the engine variation are kept the same conditions to examine both type of transmission. And evidence the potential of fuel economy improvement of CVT and AMT.In the case of CVT vehicles, increasing the ratio range was effective in increasing fuel economy when driving at relatively high speeds without much stopping and starting, while reducing friction was effective when driving at relatively low speeds with repeated stop and goes.On the other hand, in the case of AMT vehicles, increasing the ratio range was effective in increasing fuel economy when driving at relatively high speeds without much stopping and starting. When driving at relatively low speeds with repeated stop and goes, we confirmed that achieving more efficient operation of the entire power plant is possible with a combination of increasing the ratio range, increasing the gears, and/or altering how ratios are assigned.By this examination, we could understand the key to the method of fuel economy improvement by the transmission. And this could be made one index in future development of transmission.