A mixed gas cluster ion beam generator may include a nozzle chamber to contain a first mixed gas which is a mixed gas that is a mix of a first gas and a second gas, a cluster nozzle to spray gas received from the nozzle chamber in a cluster form, an ionizer to ionize a gas cluster sprayed by the cluster nozzle, and an ion accelerator to emit an ion beam to the outside by accelerating the gas cluster ionized by the ionizer by generating a potential difference to the ionized gas cluster.