We measured evapotranspiration rate for tall trees, we developed a new weight scale able to measure the amount of evapotranspiration from a large, full-sized tree, and is using the large-sized scale to carry out long-term measurements comparing the evapotranspiration of individual trees and those located in forests. The amount of transpiration per unit leaf area of isolated and forest edge individuals during the summer was 1.71 times for isolated individuals. It was clarified under the condition that all the measurement time, weather condition, tree standard, tree kind, planting base were all aligned, and it was able to confirm the difference in transpiration amount due to difference in planting density by the Lysimeter method. This study considers the difference due to the arrangement of trees and isolated individuals in the forest by the measurement by the real trees for the first time by the trees of the real size growing in the city as a street tree and a park tree. From the results of this study, it was suggested that evaluating the existence effect of trees more accurately, and appropriately arranging the trees in the urban area contribute to improvement of the urban environment, especially the thermal environment effect.