This paper examined the determinants and the effects of GAP (Good Agricultural Practice) certification. The producers under GAP certification have rapidly increased in recent years. A distinctive characteristic is that these producers are concentratedly distributed in few areas. The four prefectures (Hokkaido, Shizuoka, Kagoshima and Ehime) in Japan accounted for about 68% of certified producers. Degree of recognition for GAP, the production conditions or crop structure, intention of distributors and retailers, the development of agricultural corporations and the initiatives of agricultural cooperatives (JA) are the main factors in determining the changes and regional distribution of certified producers. A comparative static analysis derived that the conditions in market/farm prices, the possibility of technical substitution for scarce resources, and income effect are critically important in determining producers’ behavior of acquiring GAP certification. The empirical works based on 3 case studies of Ehime prefecture, illustrated that GAP certification had significant effect in improving farmer’s consciousness and farm management, but not definitely clear in price and income effects, which may become a factor of restraining the increase in GAP certification. Finally, the paper discussed the issues on the credibility of diversified initiatives in GAP certification, concerns on the control of distributors over farmers, instability of JA initiatives, and the influence on organic farm product certification.
