"One day we will have to adopt a common financial policy in Europe, after having a common monetary policy," Schäuble told a conference in Frankfurt.
He spoke against a background of how to resolve the eurozone's chronic sovereign debt crisis, which is proving difficult to do because each of its 17 members has retained control over their respective financial and fiscal policies.
The German minister also took a swipe at former US Federal Reserve Chairman Alan Greenspan, who said this week that the single European currency was breaking down.
"If I were American I would ask myself if the dollar will still exist in 10 years," he quipped. It was "wrong" to believe that the euro will disappear, Schäuble said.
Greenspan told a Washington forum on Tuesday that "the euro is breaking down" and that uncertainty stemming from the process was holding back the US economy.
Greenspan said a key problem was that European banks are falling into trouble because of their huge holdings of debt of countries close to default.