A focused ion beam system includes a gas field ion source which generates gas ions, an ion gun unit which accelerates the gas ions and radiates the gas ions as an ion beam, a beam optical system which includes at least a focusing lens electrode and radiates the ion beam onto a sample, and an image acquiring mechanism which acquires an FIM image of a tip of an emitter based on the ion beam. The image acquiring mechanism includes an alignment electrode which is disposed between the ion gun unit and the focusing lens electrode and adjusts a radiation direction of the ion beam, an alignment control unit which applies an alignment voltage to the alignment electrode, and an image processing unit which combines a plurality of FIM images acquired when applying different alignment voltages to generate one composite FIM image.