PROBLEM TO BE SOLVED : To discriminate an optimum utilization method for a lease building by temporarily deciding the most suitable building by using a real estate evaluation index and then verifying and correcting the most suitable building with a land value standard as a reference.SOLUTION : This system is composed of an input means 1 for inputting the respective input data of the use district, specified floor area ratio, road width and land value standard of specified land, a temporary decision means 2 for temporarily deciding a constructible most suitable building and an effective floor area ratio by applying a correction rule for which the road width is the reference to the inputted use district and specified floor area ratio and an establishment means 3 for establishing the most suitable building and the effective floor area ratio to be outputted by an establishment rule for verifying and correcting whether or not the temporarily decided most suitable building and effective floor area ratio can be applied in the case of considering the land value standard of the specified land by using a standard construction cost prescribed beforehand corresponding to the building division of the most suitable building. Further, a building analysis means 4 for obtaining the effective building coverage and the number of floors, etc., of the most suitable building and a profit prediction means 5 for predicting rent can be added.