Abstract: Dynamic in-line mixing device for intimately mixing a product formed of at least two primary products, comprising: a casing (2) that is elongate and internally cylindrical of revolution with at least one inlet (3) for the product to be mixed and one outlet (4) for the intimately mixed product; a rotor (5) internal to and coaxial with the casing (2) and means for driving the rotor; the rotor supports a multitude of successive coaxial discs (7), each of which comprises a plurality of holes (8), and the casing supports a multitude of successive coaxial discs (10), each of which comprises a central orifice (11) for the passage of the rotor and a plurality of holes (13); the discs (7) of the rotor (5) and the discs (10) of the casing (2) alternating with one another axially and being separated from one another.