A fluidized bed apparatus comprises a chamber having a perforated floor, a spray nozzle located in the chamber above the perforated floor, whereby material to be granulated is introduced into the chamber in the form of a solution or dispersion, means for passing heated gas upward through said perforated floor, whereby solid particles of said material are formed in said chamber, particle size-reducing means outside of said chamber, whereby particles larger than a first predetermined size are reduced in size, a screw shaft located above said perforated floor and communicating with said size-reducing means, whereby particles are withdrawn from said chamber and conveyed to said size-reducing means, a pipe having one end located downstream of said size-reducing means and its other end communicating with said chamber, and means for generating a flow of air whereby particles smaller than a second predetermined size exiting from said size-reducing means are returned through said pipe to said chamber.