The invention relates to a method for preparing lead (212) for medical use. This method comprises the production of lead (212) by the decay of radium (224) in a generator comprising a solid medium to which the radium (224) is bound, followed by the extraction of the lead (212) from the generator in the form of an aqueous solution A1, characterised in that the lead (212) contained in the aqueous solution A1 is purified from the radiological and chemical impurities, also contained in said aqueous solution, by a liquid chromatography on a column. The invention also relates to an apparatus specially designed for automated implementation in a closed system of said method. It further relates to lead (212) produced by means of this method and this apparatus. Applications: manufacture of radiopharmaceuticals based on lead (212), useful in nuclear medicine for the treatment of cancers, particularly by a-radioimmunotherapy, or for medical imaging, in both humans and animals.