Janowicz later admitted he "went nuts" during the incident Wednesday, footage of which quickly circulated on the Internet.
"Sometimes it happens like this. Sometimes I have a problem to control my emotions, but I'm trying to work on this," he said.
An International Tennis Federation official told AFP the fine had been levied for unsportsmanlike conduct.
Janowicz's outburst follows a temper tantrum by Marcos Baghdatis last year at the Australian Open, when the seething former finalist smashed four racquets in quick succession during a changeover.