The incorporation of modular production into the European and American automotive industry reached full steam in the latter half of the 1990s, and a review of individual cases shows differences in modularization methods depending on company strategy and industrial location. Moreover, depending on the modularization method, adverse effects from technological black boxes also have become noticeable. Through a comparative analysis of modular factories, this paper elucidates the development and results of modular strategies of European and American manufacturers as well as possible issues.