An ultra-minute microscope for spectroscopy includes a rod-shaped lens having an index of refraction distribution gradient and capable of having a sample mounted on one end surface thereof, an element for projecting a laser beam into the rod-shaped lens from another end surface thereof and converging it to a focal point at an interface region between the one end surface of the rod-shaped lens and the sample, and a scanner for varying the incidence angle of the laser beam to scan the focal point two-dimensionally on the one end surface.