A process for producing an .alpha.-hydroxyketone represented by formula (I): ##STR1## wherein R.sup.1 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, or an alkoxycarbonyl group; and R.sup.2 and R.sup.3 each represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aralkyl group, provided that they do not simultaneously represent a hydrogen atom; or a pair of R.sup.1 and R.sup.2, a pair of R.sup.1 and R.sup.3, or a pair of R.sup.2 and R.sup.3 is taken together to form a ring; and the pair of R.sup.1 and R.sup.2 and the pair of R.sup.2 and R.sup.3 may form a ring simultaneously, is disclosed, comprising reacting a compound represented by formula (II): ##STR2## wherein R.sup.1, R.sup.2, and R.sup.3 are as defined above, with an oxidizing agent in the presence of a ruthenium compound and water. .alpha.-Hydroxyketones useful as physiologically active substances are produced with good selectivity and in high yield.