An atomizer includes a top cover, a bottom seat, and an atomizing assembly mounted between the top cover and the bottom seat. The top cover includes a mouthpiece and a liquid injection member mounted on one end of the mouthpiece. The atomizing assembly includes a first pressing ring and a fixing member fixed on one end of the first pressing ring. The fixing member is sleeved on the liquid injection member, and the liquid injection member is able to move along an axial direction of the atomizer, to cause the liquid injection member separating apart from the first pressing ring for adding cigarette liquid. An aerosol generating apparatus with the atomizer is also provided.