This invention relates to a method for the thermal treatment of granular solids in a fluidized-bed reactor (1), in which microwave radiation from a microwave source (2) is fed into the reactor (1), and to a corresponding plant. To improve the utilization of energy and the introduction of the microwave radiation, a first gas or gas mixture is introduced from below through a preferably central gas supply tube (3) into a mixing chamber (7) of the reactor, the gas supply tube (3) being at least partly surrounded by a stationary annular fluidized bed (8) which is fluidized by supplying fluidizing gas. The microwave radiation is supplied to the mixing chamber (7) through the same gas supply tube (3).