PURPOSE: To feed several types of ion beams simultaneously, and also feed ion beams through changing their types frequently by providing a feeder with a plurality of ion sources, an ion outlet electrode, a plurality of electrodes which apply voltage between the two individually, and one magnet for selecting mass.

CONSTITUTION: A plurality of ion sources 11aW11c, whose emission ports are in the same side, and opposite to a common outlet electrode 12, are supported by means of an insulator 21 integrally. The outlet electrode 12 is grounded, and then, shielding plates 22 shield the ion sources from each other. From power sources 13aW13c is applied voltage to the ion sources 11aW11c individually, and ion beams 14aW14c are injected into a common magnet 15, and then, deflecting electrodes 23aW23d hold a stream of ion beam one after another and cause it to converge upon one point on the surface of a sample 24. A deflecting electrode group 25 is controlled by means of circuits 26 to perform scanning, and, if necessary, an accelerator 27 is used, and to the ion-source outlets are attached shutters 28 which are capable of opening and closing. If a magnetic field B and an outlet voltage V are selected, ions with a different mass M can be selected from among the ion sources 11aW11c.