Device for generating and distributing microwaves in rotary heat application systems, comprising: - an essentially cylindrical rotating drum which in turn comprises: - a side wall with at least one group of through slots; - annular extensions projecting from an external face of the side wall; - a front closure; and - a rear closure; which delimit an internal housing intended to house an element to be heated, and where each group of slots is located between two consecutive annular extensions; - at least one microwave emitter; - at least one fixed microwave filter, without direct contact with the rotating drum, made up of a cylindrical body of metallic material, for outer covering of a sector of the side wall of the rotating drum in which a group of slots is located; and - a fixed external structure that supports the above elements; the device being characterized in that the microwave filter comprises: - at least one through hole for insertion of the microwave emitter; - an external face, for fixing the microwave emitter; and - an internal face, opposable to the external face of the side wall for covering the group of slots, comprising at least one band-eliminating filter; so that in the device a partially mobile slotted waveguide is formed, delimited by: - the external face of the side wall of the rotating drum, with the slots; - the internal face of the microwave filter, with the band-eliminating filter; and - two opposing faces of two consecutive annular extensions. - an essentially cylindrical rotating drum which in turn comprises: - a side wall with at least one group of through slots; - annular extensions projecting from an external face of the side wall; - a front closure; and - a rear closure; which delimit an internal housing intended to house an element to be heated, and where each group of slots is located between two consecutive annular extensions; - a side wall with at least one group of through slots; - annular extensions projecting from an external face of the side wall; - a front closure; and - a rear closure; - at least one microwave emitter; - at least one fixed microwave filter, without direct contact with the rotating drum, made up of a cylindrical body of metallic material, for outer covering of a sector of the side wall of the rotating drum in which a group of slots is located; and - a fixed external structure that supports the above elements; the device being characterized in that the microwave filter comprises: - at least one through hole for insertion of the microwave emitter; - an external face, for fixing the microwave emitter; and - an internal face, opposable to the external face of the side wall for covering the group of slots, comprising at least one band-eliminating filter; - at least one through hole for insertion of the microwave emitter; - an external face, for fixing the microwave emitter; and - an internal face, opposable to the external face of the side wall for covering the group of slots, comprising at least one band-eliminating filter; so that in the device a partially mobile slotted waveguide is formed, delimited by: - the external face of the side wall of the rotating drum, with the slots; - the internal face of the microwave filter, with the band-eliminating filter; and - two opposing faces of two consecutive annular extensions. - the external face of the side wall of the rotating drum, with the slots; - the internal face of the microwave filter, with the band-eliminating filter; and - two opposing faces of two consecutive annular extensions.