The purpose of this paper is to analyze sustainability issues of Japan's fiscal policy and then to discuss the debt management policy based on the maturity structure of government bonds using theoretical models and numerical studies. We also investigate the desirable coordination of fiscal and monetary authorities toward fiscal reconstruction. Given the present maturity structure of bonds, Japan’s debt management policy should be based on the smoothing rule over time as follows. As the termination date concentrates within a ten-year period, it is preferable to reserve the fiscal resources to a certain extent even if the reliance on government bonds will rise temporarily. It is also necessary to reduce reliance on the government bonds gradually when there are relatively a few expiring bonds. Moreover, it is indispensable to restrain the increasing trend of reliance on government bonds.