There is provided an aerosol generating apparatus which is capable of generating aerosol stably. The aerosol generating apparatus includes a container which mixes a particulate material and a carrier gas to generate a fluidized bed of the particulate material; an aerosol delivery tube which sucks a part of the fluidized bed to deliver the part as an aerosol containing the particulate material and the carrier gas; an optical sensor which measures a position of the fluidized bed; and an adjusting unit which adjusts the position of the aerosol delivery tube based on an information about the position of the fluidized bed measured by the optical sensor. By moving an end of the aerosol delivery tube horizontally along and relative to the top surface of the fluidized bed, it is possible to avoid harmful effect that particle size distribution in the fluidized bed becomes locally non-uniform.