The introduction of CBDC is expected to make extensive changes to the financial markets, the financial industries, and the composition of shortterm assets held by the private sector, thereby affecting the implementation and the transmission mechanism of monetary policy. In this regard, this paper analyzes the impact of CBDC introduction on the reserve market, central bank balance sheet, and seigniorage, with the aim to contribute to stable and secure policy operations. Rather than building a new general equilibrium model that structurally reflects CBDC demand, we evaluate and investigate the effects of the introduction by realistically expanding a simple money multiplier model to enable intuitive scenario-based analyses.