The present invention pertains to: a method for preparing a catalyst for ammonia decomposition using cation-anion double hydrolysis; the catalyst; and a method for producing hydrogen through ammonia decomposition using the catalyst, wherein a catalyst for ammonia decomposition for hydrogen production, in which nickel (Ni) is supported on an aluminum oxide support or an aluminum composite oxide support doped with a promoter metal (M), is prepared using a ONE POT cation-anion double hydrolysis (CADH) method.