A moistening nozzle of a paper web comprises a frame into which air and water are fed. Inside the frame there is arranged a water nozzle wherewith water is conducted to an outlet of the moistening nozzle and an air nozzle wherewith air is correspondingly conducted to the outlet. The air nozzle and the water nozzle are arranged one within the other such that the air and the water form water mist that is sprayed out from the moistening nozzle. The air nozzle is provided with a thread that brings the air in swirling motion. The air nozzle comprises a sleeve part with an opening through which air is discharged and in said opening there is arranged a piece that is an integral part of the frame of the moistening nozzle, whereby a part of the moistening nozzle frame forms an inner edge of the air gap provided by said piece and the sleeve part.