The present invention provides a method for producing a hydrazine derivative of the formula [2]: ##STR1## wherein R.sup.1 is alkyl group having 1-12 carbon atoms and the like, R.sup.2 is alkyl group having 1-12 carbon atoms and the like, and Ar is phenylene group and the like, from a hydrazone derivative of the formula [1] ##STR2## wherein R.sup.1, R.sup.2 and Ar are as defined above, in the presence of at least one base selected from the group consisting of an organic base and an inorganic base, and a metal hydrogenating catalyst. By this method, reduction proceeds selectively and a hydrogenolysis reaction (side reaction) can be suppressed.