A system for generating hydrogen includes an ammonia decomposition bed configured to introduce an ammonia gas, decompose the ammonia gas into a high-pressure first mixed gas including nitrogen and hydrogen, and discharge the high-pressure first mixed gas; an ammonia adsorption bed supplied with the high-pressure first mixed gas from the ammonia decomposition bed, and configured to adsorb ammonia of the first mixed gas, and discharge a high-pressure second mixed gas including nitrogen and hydrogen; and a nitrogen adsorption bed directly supplied with the high-pressure second mixed gas from the ammonia adsorption bed, and configured to adsorb the nitrogen, and discharge the hydrogen.