A method for producing an .alpha.-alumina powder is provided. T method for producing an .alpha.-alumina powder comprising steps of: (1) pulverizing a metal compound having a full width at half maximum (Ho) of a main peak in XRD pattern to obtain a seed crystal having a full width at half maximum (H) of the main peak in XRD pattern in the presence of pulverizing agent, (2) mixing the obtained seed crystal with an aluminum salt, (3) calcining the mixture, and wherein a ratio of H/Ho is 1.06 or more.