To produce lauryl lactam in a high yield without releasing sulfur dioxide and without hydrolyzing a part of the oxime and the lactam by the photonitrosation reaction of cyclododecane and the Beckmann rearrangement of the obtained oxime in the presence of methane sulfonic acid.

This method for producing lauryl lactam comprises (A) subjecting cyclododecane, a nitrosation agent (for example, includes nitrosyl chloride and is preferably adjusted in a concentration of 0.1-25 g/L) and hydrogen chloride (excessively introduced in the form of anhydrous gas in an excessive amount based on the nitrosation agent) in an organic solvent to a photochemical reaction (the irradiation is carried out using a mercury or sodium lamp emitting light having wavelengths of usually 500-700 nm, preferably 565-620 nm, preferably at -20 to 40°C under vigorous stirring) to produce cyclododecane oxime, and subsequently (B) subjecting the obtained oxime to a Beckmann rearrangement reaction (generally at 120 to 180°C for 2 min to 1 hr under vigorous stirring).