An alumina particle (1) of the present invention has an alumina body with a short axis length (b) of 1 to 10 nm, a long axis length (a) of 20 to 400 nm and an aspect ratio (a/b) of 5 to 80. The alumina body is expressed by a Formula I, and n is not less than 0. Al.sub.2O.sub.3.nH.sub.2O Formula I