The invention relates to a molding device (1) and a method for the manufacture of structured or semistructured composite components comprising a polymer resin (50) and a fibrous substrate (51). According to the invention, the device comprises a mold (2) comprising a bottom and a lateral surface, a part (10) that is movable along the lateral surface of the mold, comprising a compression surface (14) forming a cavity (7) with the bottom and the lateral surface (5) of said mold (2), characterized in that the movable part (10) comprises a vacuum-drawing channel (13, 23) opening into a chamber (25, 42) located above the cavity and communicating with said cavity (7).