Queensland's new Arts and IT Minister Ian Walker has been sworn in at a ceremony at Government House in Brisbane.
Ms Bates cited health reasons for her decision.
Late last year, Dr Bruce Flegg was replaced as housing minister after discrepancies with his lobbyist register and diary.
Premier Campbell Newman says Mr Walker will do a "sensational" job.
"He will, I believe, fulfil the very highest expectations of this office," he said.