Abstract: A device for braking lines of tying twine, for agricultural machines, of the type of balers, round balers and the like. Such machines are provided with assemblies for tying bales of previously-cut agricultural products, of the type of grass, wheat, maize, hay, forage, and the like. The braking device comprises an electronic unit for controlling and managing at least one actuator (2) for moving at least one braking element (3), which is actuated by the electronic unit by way of the actuator (2), in order to retain at least partially at least one respective length of at least one line of twine (A), during its unreeling.