Öz In this study, potential benefits and costs of monetary union have been explained. The most important cost element of monetary union is that countries can't apply an independent monetary and exchange rate policy because of monetary union. At the same time both decreasing of transaction costs and disappearing of exchange rate uncertainities because of monetary union will directly or indirectly create effects that increase welfare of member countries. Monetary union has ben assetmented points of view of Monetarist and Keynesian by using cost-benefit curves. It has been concluded that monetary union can provide important benefits for member countries.