An injector of a flotation cell, the injector comprising a feed pipe for feeding a fiber suspension flow into the flotation cell, a mixing apparatus for mixing air into the fiber suspension flow and at least one air feed connection arranged before the mixing apparatus for feeding air into the injector. The injector further comprises a nozzle section which is arranged before the mixing apparatus and comprises an aperture plate provided with apertures and nozzles fixed to the aperture plate substantially at the apertures after the aperture plate, there being open spaces between the nozzles. The air to be fed from the air feed connection is arranged to flow into the spaces between the nozzles and further into the mixing apparatus with the partial flows of the fiber suspension flow entering from the nozzles.