District-based agricultural income level, which is a criterion of District Suitability Classification, is a macroscopic indicator of agricultural landuse suitability. Locational conditions have brought not a little influence to the agricultural income level. In this paper, the authors try to make it clear how the agricultural income level has been influenced by the locational conditions, namely, accessibility to urban center, natural condition and inclusive urbanization level.
A causal model of the locational conditions to the agricultural income level is defined and tested with statistical data from Agricultural Census Card (1980) . The study area is the Suwa Region in Nagano Prefecture. The results from a path analysis show that the inclusive urbanization level has the strongest direct effect toward the agricultural income level. Direct control measures to the urbanization such as revise of legal landuse plan are considered to be the most effective for conservation of agricultual good land in this region. The results also show that the total effect of natural condition is the strongest among the locational conditions. So the physical land suitability conditions should be attached much importance in revising landuse plan.