A wafer transfer apparatus includes a robot arm and a robot arm cleaning device that injects purge gas into a vacuum nozzle of the robot arm under a normal stand-by state wherein the robot arm does not suction a wafer, to clean the vacuum nozzle. The robot arm cleaning device comprises a solenoid valve adapted to supply and intercept air, a first air valve adapted to selectively maintain and release a vacuum state in response to the air supplied from the solenoid valve, and a second air valve adapted to selectively supply and intercept a purge gas in response to the air supplied from the solenoid valve. The robot arm holds a wafer by a vacuum state of the vacuum nozzle when the first air valve is opened, and the vacuum nozzle is cleaned by the purge gas supplied when the second air valve is opened.