The existence of magnetic domain has been known for a long time, and its importance is further growing because of rapid storage density increase of recording media. Magnetic domain observations made it possible to derive the microscopic magnetic parameters such as the magnetic anisotropy and the domain wall energy connected with exchange interaction in addition to the size of magnetic domain. Among the various methods for observing the magnetic domain, scanning probe microscopes are powerful tools owing to the user-friendliness and the flexibility to sample specimen and measurement environment. These instruments enable us to evaluate three dimensional magnetic domain structure and to explore novel magnetic materials in a high throughput way. Here, we show the results obtained from the measurements of ferromagnetic semiconductors, Mn doped GaAs and Co doped TiO₂ thin films, and a colossal magnetoresistive material, La_1−xSr_xMnO₃ composition-spread film.