A new figure correction method is applied to fabricate an elliptical mirror to realize a one-dimensionally diverging X-ray beam having high image quality. Mutual relations between figure errors and intensity uniformities of diverging X-ray beams are also investigated using a wave-optical simulator and indicate that figure errors in relatively short spatial wavelength ranges lead to high-contrast interference fringes. By using the microstitching interferometer and elastic emission machining, figure correction of an elliptical mirror with lateral resolution close to 0.1mm was carried out. A one-dimensional diverging X-ray obtained by the fabricated mirror was observed at SPring-8 and evaluated to have a sufficiently flat intensity distribution.