In this paper, we estimate the investment function with Tobin's q utilizing cross-section data of basic survey on small and medium-sized enterprises (SMEs) investigated from 2007 through 2014 (actual values from FY2006 to FY2013). We consider internal reserves (cash flow) and debt ratios, which influence firms'financing. The results of empirical analysis are as follows. For SMEs with high debt ratios, it was relatively difficult to finance for investment with debt under the safety net guarantee system. After FY2012, investment in the construction industry was raised by and large; however, construction firms with high debt ratios were faced with the problem of financial constraint. Furthermore, in three major metropolitan areas, the existence of the debt overhang hypothesis is shown after the global financial crisis. In the revised Small and Medium-sized Enterprise Credit Insurance Act, it is established that credit guarantee corporations and financial institutions in the same local area must work together. This effort is expected to reduce such disparities between areas.