The invention relates to a method for purifying a supply gaseous flow containing at least 5 vol. % of N2O and oxygen, in which: (a) the gaseous flow is contacted with a main adsorbent (3) including at least one zeolite exchanged at more than 50% by one or more metal cations and having an N2O adsorption capacity, as measured under 1 bar and at 200° C., of more than 80 Ncm/g in order to adsorb at least a portion of the N2O from said flow and to produce a purified gaseous flow; and (b) recovering a purified gaseous flow having an N2O content lower than the N2O content of the supply gaseous flow contacted with the main adsorbent during step (a).