Scanning near-field optical microscope (SNOM) was applied to the formation of ultrasmall phase change domains to investigate the feasibility of ultrahigh density data storage. Phase change domains ranging 60 - 100 nm in diameter, which is far beyond the diffraction limit, could be successfully written in amorphous GeSbTe recording film by point heating with pulsed laser light (λ=785 nm, 7 mW, 0.5 ms) through the optical fiber probe whose aperture size was nearly 50 - 100 nm. The detected power in observation of these recorded domains is 10 2 - 10 3 times as high as that in magneto-optical observation. It indicates that phase change recording with SNOM has a potential to achieve ultrahigh density data storage (more than 100 Gb/in 2 ) with high signal detection efficiency.