Provided is a sample milling apparatus capable of milling various samples efficiently. The sample milling apparatus includes an anode, a cathode for emitting electrons which are made to collide with gas molecules so that ions are generated, an extraction electrode for causing the generated ions to be extracted as an ion beam, and a focusing electrode disposed between the cathode and the extraction electrode and applied with a focusing voltage. The spatial profile of the ion beam is controlled by varying the focusing voltage applied to the focusing electrode.