Experiments on measurement of psychological quantity were made, with using photomontage slidefilms of street-vistas and by introduction of a new structual model of psychological evaluation, and the possibility that psychological quantity is connected to simple physical quantity, is shown. The objects in experiment were black and white photomontage slidefilms. After obstructive elements (i.e. utility poles, billboards, and original roadside trees etc. ) retouched, roadside trees were montaged. Experiments were made into tow parts. At part 1, backgrounds, trees, planting arrangements on the objects were changed and in part 2, width of road and planting arrangements, too. After t-test, F-test and variance analysis, it was found that there was no significant difference in experimental conditions, and the effect of background was small. Applying the new model with 2 turning points on response continuum to the results of these experiments, the best interval of plantings was calculated on each case. Lately the following are concluded ; 1. The best width of planting exist on "evaluation" scale. 2. The best interval of planting changes according to height of trees, but in regular height, there is no significant differences in trees and backgrounds. 3. The best interval of planting in "evaluation" scale is a few over 10m. 4. Platanus-6m is the most preferable. 5. The logarithm of the density of planting is the most suitable parameter for explaining of psychological quantity, and, the relation between stimulus and judgement corresponds to Weber-Fechner's theory. 6. For the plane stimulus as slidefilms, the subjects grasp them solidly. The fact shows high perceptual constancy of human.