The purpose of this paper is to supplement the ‘self-sufficient earthenware production theory’ of the Proto-Three Kingdoms period and to enhance the understanding of the daily earthenware production system in Mahan, Yeongsan River region. Considering the characteristics of Mahan society, in which a large number of communities or polities co-existed, the production organization and level of specialization were identified for simbal(‘deep bowl’) ware, a representative daily earthenware. First, the discussion on household economy and production specialization was reviewed, and provisional hypotheses were established based on this, and then verified through standardization analysis at local and settlement levels, respectively. In order to guarantee the objectivity of standardization analysis as much as possible, scientific analysis methods such as Geometric Morphometrics(GM) was used. The results of the analysis indicate that in the Mahan society of the Yeongsan River region in the Proto-Three Kingdoms to Three Kingdoms period, simbal ware was professionally produced in specific households and workshops in several villages in the local area, and then shared within the community; that is, ‘product specialization’ was achieved. In addition, it could be observed that Type B simbal ware is more clearly differentiated at the local level than Type A simbal ware, which preceded it. On the other hand, in areas such as Gwangju where urbanism had been developing since the Proto-Three Kingdoms period, it appears that the spread and diffusion of manufacturing technology or the exchange and distribution of products was actively carried out among the villages where exchanges were frequent due to the development of specialization and exchange networks. The fact that similarity between settlements can be confirmed for the forms of Type A simbal ware, which had been popular prior to the 4th century, indicates that the possibility that the Gwangju area had been a place of ‘production specialization’ since the Proto-Three Kingdoms period should be considered.