Recently, reckless exploitation of land resources without much consideration for the environmental value of the land has been witnessed to accommodate the ever-increasing demands for regional development. Fragmentation due to land development is a major reason for the declining biodiversity in forest ecosystems. The purposes of this study were (1) to investigate the relationship between the factors of land development and forest fragmentation in 13 watersheds of a metropolitan area and (2) to suggest a forest management plan through the relationship. We carried out a factor analysis to determine explanatory axes of forest fragmentation, and then conducted a correlation analysis between the factor scores and the factor of land development, such as the rate of built-up areas, road density, number of built-up patches, and area of housing developments. The first explanatory axis represented stability of landscape highly related with the rate of the built-up area and road density. The second axis represented the level of fragment highly related with a number of built-up patches. Forest fragmentation patterns of the 13 watersheds were classified for the similarity in forest fragmentation. This study presents the forest management plans including distribution and level of land development and forest conservation.