Hundreds of police officers and investigators in different regions have worked for years to try to solve the killings.
The 68-year-old man was arrested in Mulhouse in northeast France on Tuesday, according to a judicial official who was not authorized to speak to the media. The victims included male and female prostitutes killed by violent blows to the head.
Prosecutors suspect the man of involvement in 11 killings in the Alsace region, four in the neighboring region of Franche-Comte, and three near Paris, the official said. The killings took place between 1980 and 2002.
While the man is suspected in 18 cases, his arrest was the result of a judicial inquiry into just six of the killings, a police official said.
Prosecutors believe the man worked with an accomplice, a 43-year-old currently serving 20 years in a prison in Poissy west of Paris for the murder of an insurance agent.
The daily newspaper L'Alsace reported that the two men targeted primarily gay victims, and that the man arrested Tuesday worked as a transvestite performer in cabarets in Alsace and neighboring Germany.