A method for producing .alpha.-alumina powder is described. The method comprises the steps of removing water from a compound containing the following (1), (2), (3) and (4), and calcining the results: (1) .alpha.-alumina precursor, (2) seed crystal, (3) water, (4) nitrate ion in an amount of from 2.8 to 3.3 mol per mol of aluminum (Al) contained in the .alpha.-alumina precursor and the seed crystal.