Authorities said he had gone to a mall to meet a 14-year-old girl he thought he had met during an online chat. However, a state agent had posed as the girl, and the 51-year-old mayor was arrested at the mall in suburban Milwaukee.
The charges include attempted second-degree sexual assault of a child under 16, possession of child pornography, child enticement, use of a computer to facilitate a child sex crime, attempt to expose a child to harmful material and misconduct in office.
Investigators found records of 1,800 sexually explicit chats on Becker's computer.
It all started after city workers, who helped Becker fix a problem with his personal computer, found pornography files on it and alerted Racine police who passed the case on to state investigators to avoid a conflict of interest.
Becker was elected mayor in 2003 and ran unopposed for re-election in 2007. The Democrat had previously served two terms as a city alderman.
Racine is Wisconsin's fifth-largest city, with about 80,000 residents. It sits on Lake Michigan about 30 miles south of Milwaukee.