A production method of amorphous silicon oxide powder comprises a step of preparing a wood, agricultural crop or plant containing hexose and/or pentose and silicon oxide as a starting raw material, a step of hydrolyzing the starting raw material with nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid or organic acid to reduce a content of the hexose to 10% by weight or less and/or a content of the pentose to 20% by weight or less, and a step of burning residue yielded in the hydrolyzing step at a temperature of 400° C. to 1200° C.
