The specifications of UVSOR-III photoelectron momentum microscope are summarized. The momentum microscope opens the door to direct observation of the Fermi surface and band structure of µm-sized targets such as surface atomic sites, thin films and interfaces, molecular adsorbates, and polycrystals. The momentum-resolved micro-photoelectron spectroscopy realized by this system is an important method for developing nanomaterial science and quantum device engineering through electronic structure analysis. One can investigate how the composition, structure, and electronic state of materials are related to electronic properties and functions. It enables electronic property and function analysis from a new point of view, such as direct observation of structure and electronic state changes where superconductivity and catalytic activity are occurring.