In this study, we evaluated the pattern of agricultural landscape mosaic in Niigata Prefecture using the Satoyama Index (SI), which is a simple index composed by agricultural landscape heterogeneity and the ratio of nonagricultural land cover. At first, land cover map based on LANDSAT imagery was classified by supervised classification method. Next, we calculated landscape heterogeneity among the 400 grid cells (20 × 20 grid cells: 600m×600m) comprising each agricultural landscape unit from the agricultural landscape heterogeneity index (ALHI). We obtained index values by multiplying the ALHI by the proportion of grid cells classified as nonagricultural landscape elements without urban within the basic landscape spatial unit. SI value was high in the bordering area between slope and flat area such as edge zone of forested area and agricultural lands. In addition, SI value was high also in the portions of along the main river or the coastal forests. There was no inconsistency in the number of landscape elements and SI value within the spatial unit by comparing the spatial pattern of land cover and the SI value. Since SI evaluates the heterogeneity in the agricultural landscape, SI showed zero in the homogenized area such as the broad-leaved deciduous forests. From our results, we pointed out that SI can just quantify the degree of heterogeneity of agricultural landscape, and it is inappropriate to evaluate the biodiversity in a region only with SI value.