whose widths are 5–40 µ m, are used for this fitting. This is because gadolin- ium cannot enter trenches narrower than 5 µ m in the spattering process. In the fitting result, the horizontal and vertical resolutions are evaluated $^{to be 2.9}$± 0.1 µ $^{m and 4.3}$± 0.2 µ m, respectively. These values correspond $^{to 6.9}$± 0.2 µ $^{m and 9.9}$± 0.3 µ m of the full width at half maximum of the line spread functions. This difference is caused by the difference in the full well capacity. The measured spatial resolution is much finer than the pixel size of 24 µ m. We developed a pixel detector for UCN which has high spatial resolution with temporal information. The detector is based on a commercial CCD on which a suitable neutron converter is directly evaporated. $^{10}$B and $^{6}$Li are tested as neutron converter materials. We conclude that $^{10}$B has better properties as a neutron converter material. Using $^{10}$B, the UCN detection $^{efficiency is 44.1}$± 1.1%. Our UCN detector can measure the UCN incident $^{position with a precision of 2.9}$± 0.1 µ $^{m (horizontal) and 4.3}$± 0.2 µ m (ver- tical) in terms of sigma of the error functions. We are indebted to Prof. H. M. Shimizu of the High Energy Acceler- ator Research Organization (KEK) for constructive comments and encour- agement. We would also like to thank Prof. P. Geltenbort of Institut Laue– Langevin (ILL) and Prof. S. Tanaka of Tohoku University for their technical 17 5. Summary 6. Acknowledgment