Ammonia is catalytically produced from a nitrogen-hydrogen mixture. First of all, a vaporous feed mixture, which comprises 30 to 60 vol-% methanol and 40 to 70 vol-% steam and has a volume ratio steam:methanol of 1 to 3, is passed through at least one bed of a breakdown catalyst at pressures in the range from 30 to 200 bar, the temperatures in the catalyst bed lying in the range from 200 to 500.degree. C. From the catalyst bed, a first gas mixture is withdrawn, which, calculated dry, comprises 40 to 80 vol-% H.sub.2 and 10 to 30 vol-% CO.sub.2. The first gas mixture is cooled, CO.sub.2 is removed in a gas cleaning, and a second gas mixture is generated, which comprises at least 95 vol-% nitrogen and hydrogen, and which is supplied as synthesis gas to an ammonia synthesis for the catalytic production of ammonia.