The maturity structure of external public debt plays a central role in sovereign debt management by shaping refinancing risk, borrowing costs, and fiscal sustainability. Although dynamic stochastic general equilibrium (DSGE) models have been widely used to analyze macroeconomic dynamics, their application to sovereign debt maturity choice remains limited. This paper contributes to the literature by developing a DSGE framework in which the optimal maturity structure of external public debt emerges from the interaction between international investors, the central bank, and the government. International investors determine financing conditions according to global financial conditions and sovereign risk, the central bank influences borrowing conditions through monetary policy and reserve adequacy, and the government optimally chooses debt maturity by balancing financing costs against refinancing and sovereign risks. Simulation results indicate that both macroeconomic and sovereign-specific shocks generate significant adjustments in investor demand for long-term debt and the government's optimal maturity decisions. The findings highlight the importance of integrating macroeconomic conditions, monetary policy, and sovereign risk into a unified framework for analyzing debt management and provide policy insights for improving debt resilience and reducing refinancing vulnerabilities.