For the purpose of investigating the posibility of natural environmental survey using Landsat data, an experimental study on the estimation of vegetal naturalness and its accuracy was carried out. The vegetal naturalness, which is the measure for evaluating the degree of human land renovation using the combination of vegetal groups, was used in “Natural Census on Vegetation” by the Environmental Agency of Japan. In this study, Hiki-hill in Saitama-prefecture was selected as a test area, and the vegetal naturalness degree map was produced through land cover classification procedure using Landsat data. As the second step, the degree map was deviled into meshes and the occupation ratio of every degree of naturalness in each mesh was calculated as well as weighted naturalness, which was defined as average naturalness obtained from the combination of all degrees in a mesh. The occupation ratio and the weighted naturalness were also calculated from the vegetation map of the test area. Finally, the two indexes obtained from Landsat data were compared with those obtained from the vegetation map respectively, and the accuracy of the estimation of naturalness by Landsat was discussed. Although the accuracy of the estimation of individual distribution of naturalness within a mesh was not sufficiently high, a fairly good correlation of 0.872 was obtained between the weighted naturalness from Landsat and that from the vegetation map, which showed the high reliability of Landsat data for estimating the average naturalness of a mesh. The result of this study may suggest a pilot approach in order to utilize Landsat data for the evaluation of natural environment.