An ion beam machining and observation method relevant to a technique of cross sectional observation of an electronic component, through which a sample is machined by using an ion beam and a charged particle beam processor capable of reducing the time it takes to fill up a processed hole with a high degree of flatness at the filled area. The observation device is capable of switching the kind of gas ion beam used for machining a sample with the kind of a gas ion beam used for observing the sample. To implement the switch between the kind of a gas ion beam used for sample machining and the kind of a gas ion beam used for sample observation, at least two gas introduction systems are used, each system having a gas cylinder a gas tube, a gas volume control valve, and a stop valve.