Abstract
Minimum lot area is one of the Group standards of the Building Standards Act. It has been established as a means to suppress the
mini development by fragmentation of the land, and suppress the adverse impact (external diseconomy) on the living environment
due to the building, such as sunlight and ventilation. In this paper, I focus on tightening of regulations of the minimum lot area. I
analyzed by DID (Difference-In-Difference), to clarify the inhibitory-effect of external diseconomies due to household density as a
policy objective. And then I analyzed by hedonic approach about the impact on land prices and detached housing market. As a
result, I made it clear, that the impact of external diseconomy by household density can not be confirmed. Other hand, I made it
clear, that land prices in regulatory region has fallen and market trading price of detached houses are distorted. It is thought that
regulations interfere with the highest and best use of land.
