"I hope that we can convince (the) UK... (to) stay in the EU, because a Brexit would be a disaster for the UK and for Europeans," Schäuble said during a discussion with students at Sciences Po university in Paris.
Schäuble also said that he hoped Britain would join the euro in the coming years.
"It will take some time," he said.
British Prime Minister David Cameron is seeking to renegotiate the terms of Britain's EU membership before holding an in/out referendum by the end of 2017.
Cameron has said he will push for broad changes including protecting sovereignty, opting out of the EU's commitment to "ever closer union", limiting access to benefits for migrants, and boosting competitiveness.
Until recently, opinion polls suggested that those against a so-called "Brexit" were in the majority, but two recent surveys have put the anti-EU camp ahead.