Revision of the Productive Green Land Act in 1992 and the related taxation system affected urban farmer decisions on long-term land use.　The purpose of this paper is to clarify factors affecting the land use by urban farmers through changes in farm household economy, especially characteristics of business, land tax and land price.　We illustrate how changes in land use influence the farm household economy. Structured interviews were conducted with three urban farmers in Nerima Ward on the details of their business in July 2014.　The economic performances for land use of each farmer were analyzed by calculations of net present return in land not only with the same method used in previous studies but also with our “Time-Varying Models” that can evaluate the effects of changes in an economic environment and taxation system. Major findings are as follows.　Productive Green Land has no negative effect on the expected acreage of land that can be sold from an urban farmer inheritance, because tax payment for the inherited land is comparatively low even when the land price is high.　In contrast, potentially developable farmland, which is taxed at the same rate as residential land, has a negative effect on the farm household economy.　Therefore, the economic performance of a parking lot highly depends on profitability and land price, whereas, an apartment rental business has a positive effect on the expected acreage of land that can be sold, because such sales benefit from special tax reductions related to both property tax and inheritance tax. We recommend that urban farmers who try to preserve their farmland should choose a land use that will positively influence their farm household economy.　Especially, potentially developable farmland and land for their home significantly worsen a farm household economy. JEL Classification:Q15, R14