A method for preparing an aldehyde of general formula (II): where R is a linear hydrocarbon chain of formula C n H 2n-2p+1 , with: - n which is a natural number ranging from 9 to 24, - p corresponding to the number of unsaturations of the hydrocarbon chain which is an integer ranging from 1 to 4; said method is continuous and comprises the following concomitant steps: a) feeding a continuous reactor under oxygen pressure of between 1 and 30 bar with: i) an alcohol of general formula (I): where R, n and p are as defined previously for the compound of formula (II), in solution in an apolar organic liquid phase (A) with a density strictly less than 0.7, ii) a copper-based catalyst in solution in a polar liquid phase (B) with a density greater than or equal to 0.75, the phases (A) and (B) being immiscible with each other, the alcohol/copper-based catalyst molar ratio ranging from 0.01 to 0.5, b) recovering the aldehyde in phase (A) by liquid/liquid separation. where R is a linear hydrocarbon chain of formula C n H 2n-2p+1 , with: - n which is a natural number ranging from 9 to 24, - p corresponding to the number of unsaturations of the hydrocarbon chain which is an integer ranging from 1 to 4; - n which is a natural number ranging from 9 to 24, - p corresponding to the number of unsaturations of the hydrocarbon chain which is an integer ranging from 1 to 4; said method is continuous and comprises the following concomitant steps: a) feeding a continuous reactor under oxygen pressure of between 1 and 30 bar with: i) an alcohol of general formula (I): where R, n and p are as defined previously for the compound of formula (II), in solution in an apolar organic liquid phase (A) with a density strictly less than 0.7, ii) a copper-based catalyst in solution in a polar liquid phase (B) with a density greater than or equal to 0.75, the phases (A) and (B) being immiscible with each other, the alcohol/copper-based catalyst molar ratio ranging from 0.01 to 0.5, b) recovering the aldehyde in phase (A) by liquid/liquid separation. a) feeding a continuous reactor under oxygen pressure of between 1 and 30 bar with: i) an alcohol of general formula (I): where R, n and p are as defined previously for the compound of formula (II), in solution in an apolar organic liquid phase (A) with a density strictly less than 0.7, ii) a copper-based catalyst in solution in a polar liquid phase (B) with a density greater than or equal to 0.75, the phases (A) and (B) being immiscible with each other, the alcohol/copper-based catalyst molar ratio ranging from 0.01 to 0.5, i) an alcohol of general formula (I): where R, n and p are as defined previously for the compound of formula (II), in solution in an apolar organic liquid phase (A) with a density strictly less than 0.7, ii) a copper-based catalyst in solution in a polar liquid phase (B) with a density greater than or equal to 0.75, the phases (A) and (B) being immiscible with each other, the alcohol/copper-based catalyst molar ratio ranging from 0.01 to 0.5, the phases (A) and (B) being immiscible with each other, the alcohol/copper-based catalyst molar ratio ranging from 0.01 to 0.5, b) recovering the aldehyde in phase (A) by liquid/liquid separation. <EOS>