The method for preparing hydrazodicarbonamide (HDCA) using biuret as a starting material is disclosed. The method comprises the steps of; obtaining metal monohalobiuret salt by reacting a biuret with a metal hypohalogen compound, or by reacting the biuret with a halogenating agent and a base; and reacting the obtained metal monohalobiuret salt with ammonia, wherein the hydrazodicarbonamide is produced in the presence of a catalyst including bromine or iodine atom and generating bromine or iodine ion during the reaction.