Fe-Pt alloy thin films were fabricated by the ion beam sputtering method and their extraordinary Hall effect was investigated. From the relation between resistivity p and extraordinary Hall coefficient R-S. side-jump mechanism is considered to be dominant. With decreasing film thickness d, field sensitivity of Hall voltage S was found to increase, which originates from the perpendicular surface magnetic anisotropy. Hall voltage of the Fe-Pt ultra-thin film (25 A thick) shows almost constant temperature dependence in the temperature range from room temperature down to 10 K. Reduction of Curie temperature T-c. which may be the manifestation of two-dimensionality, was found for the case of 25 Angstrom thickness, compared with the sample which was 1200 Angstrom thick. Fabrication of micro Hall patterns with the pattern widths from 0.5 to 5 mum was attempted and the results of Hall measurement are presented.