A chemical mechanical polishing apparatus includes a platen having a first region configured to support a wafer, and a second region disposed outside the first region. The chemical mechanical polishing apparatus further includes a polishing pad disposed on the platen, a pad head to which the polishing pad is attached, a slurry supply configured to supply a slurry onto the wafer, and an injection port disposing on the second region of the platen. The injection port is configured to inject a predetermined gas to an edge of a bottom surface of the wafer and toward the outside of the wafer.