This paper analyzes the structure of the Japanese economy as an "economic superpower" dependent on exports and foreign demand, in terms of the reproduction schema of Marxian theory. The foundations of Japan's post-war economy were established during the period of rapid economic growth, based on an accumulation process led by "Department I" production, especially the production of capital goods and raw materials. In the mid-1970's, global recession forced Japanese industry to adjust to new circumstances, and Japanese companies gained greater international competitiveness, particularly in the automotive and electric sectors and others related to the machine industries. This was due to the adoption of "slim management" and the introduction of micro-electronics technologies. "Slim management" reduced employment and capital investment, increasing labor intensity and efficiency in order to build up capital more effectively. The significance of "slim management" for Japan's reproduction structure was that it not only realized sharp production increases and greater international competitiveness but also brought about a contraction of domestic demand in both investment and consumption. As a result, the Japanese economy became dependent on exports. Domestic demand grew more than exports from the latter 1980's into the 1990's, but the Japanese economy again became more deeply dependent on foreign demand from the late 1990's on. In the 2000's, foreign demand drove an increase in domestic output by the automotive, industrial machinery, metal products, and chemical products industries, despite the concurrent expansion of Japanese companies' electrical equipment factories elsewhere in Asia. Domestic demand showed less growth than domestic output during this period, much as it did in the second half of the 1970s, because Japanese companies in the leading industries were maintaining and strengthening their competitiveness by employing more non-regular workers (including dispatched workers, contract workers, part-time workers and others) than regular employees. The result has been the contraction of the domestic economy, because the "contradictions between production and consumption" in the domestic economy have inevitably widened in the face of ever-harsher competitive conditions worldwide. This analysis shows that as an "economic superpower" dependent on exports and foreign demand, Japan's economy has been founded on domestic wage differentials and on poverty and has brought about a condition of overproduction in the world economy.