A device including an imaging-type or a projection-type ion detection system and being capable of performing observation or inspection at high speed with an ultrahigh resolution in a sample observation device using an ion beam is provided. The device includes a gas field ion source that generates an ion beam, an irradiation optical system that irradiates a sample with the ion beam, a potential controller that controls an accelerating voltage of the ion beam and a positive potential to be applied to the sample and an ion detection unit that images or projects ions reflected from the sample as a microscope image, in which the potential controller includes a storage unit storing a first positive potential allowing the ion beam to collide with the sample and a second positive potential for reflecting the ion beam before allowing the ion beam to collide with the sample.