The Australian third seed was too strong and too consistent for the 15th-seeded Slovak as he won in 94 minutes to set up a clash with unseeded Finn Jarkko Nieminen.
Hewitt, the champion in 2001 and runner-up to Roger Federer last year, was on top from the start and raced through the first set in just 24 minutes.
Hrbaty, again wearing a bizarre shirt with two holes cut out of the back, led 3-1 in the second set but Hewitt won five of the next six games to win the set and then eased through the third to clinch a simple victory.