Abstract: This invention relates to an automatic control device adapted to regulate, without interruptions, cigarette-making process and in a substantially continuous way, the cut tobacco being re-circulated back to the distributor, as trimmed excess tobacco (S) from the uniform tobacco rod, formed in the pneumatic suction belt forming assembly (N) of a continuous cigarette-making machine. Said device substantially comprises a detector suction head (1), through which all of said trimmed excess tobacco (S) is passed pneumatically, in its path of suction re-circulation, from trimmer (R) of the belt (N) the distributor of the cut tobacco for the formation of the rod. Said detector suction head (1) is associated with a photo-cell sensor (4, 5) whose light beam is liable to be attenuated by the total flow of trimmed cut tobacco (S) sucked through said head.