The aim of this study is to investigate the structure of agricultural production function in terms of an economies of scale in Korea, China, and Japan. The Cobb-Douglas production function, production function by a relative input factor, and Ramcharran production function are employed for empirical analysis, respectively. Empirical evidence reveals that the Korea and Japan seem to systematically set up their own agricultural production systems which enable to efficiently utilizing labor and capital in their production processes. More specifically, capital is on the way for utilization in Korea, whereas capital-embodied labor force is playing a key role in Japan. And, scale economy is revealed in the Korea and Japan as well. However, not only capital is solely contributed to increase a level of agricultural output, but also scale economy is seldomly identified in China. It is mainly due to the fact that the agricultural production system in China is primitive, yet. It also has to be mentioned that the Korea and Japan could be cooperative in agricultural production and its trading by virtue of operational market mechanism. However, well-established negotiable strategies should be ready in advance to make a deal with China. The primary reason for such circumstance is that Chinese agricultural production system is heavily relied on non-economic factor.