The 40-year-old said he was guilty of the armed robberies, and admitted to an additional hold up too.
"I regret it strongly," he told journalists, adding that he'd committed the crimes because he was having financial problems. In all, the robberies yielded some €90,000.
The Schleswig-Holstein-born robber said he had entered the stores politely and quietly - a statement that has been backed up by witness reports. Two witnesses said the man had said, "I would like to have yesterday's till, please."
The man is accused of robbing the stores with a blank pistol between July 2006 and March 2008 in six German states - said to be the biggest series of retail chain robberies the country has ever seen.
Police special forces finally caught the thief in the act in the town of Bottrop on March 28 as part of their special investigation Perücke, or "wig."