Okishio's Accumulation Theory (first edition) is first published in 1967. Thereafter we have experienced a long-term low growth trend in most of advanced countries and especially severe two decades stagnation in Japan. It has led a transformation in main stream economics but their core structure remains unchanged. At the same time the heterogeneous economics has evolved into many fields. Okishio's Accumulation Theory was a very influential contribution to heterogeneous economists in Japan and has effects to wider range of economists including main stream academics. In this paper we reconsider Okishio's Accumulation Theory in the light of modern perspectives. First we present the main message of Accumulation Theory, which are summarized as the following four items. 1) historical character of capitalism, 2) disequilibrium and its unstable cumulative movements, 3) profit-led and investment-led character of capitalism, and 4) the long-run tendency of capitalistic economy. It is shown that Okishio's propositions in these four items are still relevant. Next we evaluate the post-Keynesian economic theory, especially Kaleckian model. We compare the standard Kaleckian model with the standard Okishio's accumulation model. There are some shared visions of capitalistic economy in these standard models, but distinct differences exist in setting up the investment function and therefore analyzing dynamic movements of the economy. We discuss that the standard Kaleckian model presented by Lavoie (2010) has problematic points in defining long-run economy and its setting-up of investment function. Nevertheless, there is a important contribution in recent researches following Kaleckian model. It shed light to explore the effects of distribution and accumulation on employment and growth, to examine the possibility and conditions to realize the wage-led economy in the medium run, which are the emerging area of research. There exist many unsolved issues to be analyzed in detail.