To realize a focused-ion-beam machining apparatus capable of machining a thin sample with a wide area and a uniform film thickness and a needle-like sample with a sharp tip, in a focused-ion-beam machining apparatus including: an ion source (1); an electronic lens (3) focusing an ion beam extracted from the ion source (1) and irradiating the ion beam to a sample (5); and a sample holder (13) holding the sample (5), the sample holder (13) is provided with a shield electrode (7) arranged in a manner such as to cover the sample (5), and the sample (5) and the shield electrode (7) are insulated from each other in a manner such that voltages can be applied to them separately from each other.