"Reunified Germany has accomplished great things," said de Maiziere, presenting a government report as it prepares to mark the 20th anniversary on October 3.
Reunification has been "a huge success story with a great deal of light, but of course also some darker sides," de Maiziere added.
"Today, 20 years after celebrating Germany unity, people in the west and the east can be proud of what they have achieved together since the peaceful revolution and reunification," he added.
The minister pointed to the fact that average unemployment in eastern Germany is currently at its lowest level since 1992, although still considerably higher than in the west.
And he said the fact that gross domestic product per capita in the east had reached 73 percent of that in the west "should be seen as a minor economic miracle."
Furthermore, transfers from west to east "remain valid and no one is calling them into question," insisted de Maiziere.
A survey published earlier Wednesday showed that 71 percent of Germans wanted to scrap the so-called "solidarity pact," covering transfers of funds from the west to the east, which is due to run until 2019.
Economists estimate that €1.4 trillion ($1.8 trillion) has flowed from west to east since reunification but de Maiziere declined to cite an exact figure.
He acknowledged that 2.7 million people had left the former East Germany in the past 20 years but pointed to the fact that 1.6 million people had gone the other way.
The biggest challenges still facing Germany are to reduce unemployment and boost economic output in the east, de Maiziere said.