Provided are a large-current and highly stable gas field ionization ion source, and a high-resolution ion microscope with a large focal depth. The present invention relates to an ion microscope provided with a gas field ionization ion source, in which disposed are a refrigerator for cooling the gas field ionization ion source independent of the main body of the ion microscope, and a refrigerant circulation circuit cooling mechanism for circulating a refrigerant between the gas field ionization ion source and the refrigerator. Consequently it is possible to reduce the mechanical vibration of the refrigerator, which propagates to the gas field ionization ion source, and to achieve both the improvement of the brightness of the ion source and the improvement of ion beam focusing performance.