A focused ion beam apparatus includes: a focused ion beam irradiating mechanism configured to irradiate a sample with a focused ion beam; a detector configured to detect a secondary charged particle generated by irradiating the sample with the focused beam; an image generating unit configured to generate an sample image of the sample; a processing area setting unit configured to set a processing area image including a plurality of pixels corresponding to positions of irradiation of the focused ion beam on the sample image; a position of irradiation setting unit configured to set coordinates of the pixels included in the processing area image; a beam setting unit configured to set a dose amount of the focused ion beam irradiated from the focused ion beam irradiating mechanism according to intensities; and an interpolating unit configured to perform an interpolating process on the processing area image.