A machine to manufacture cartridges for electronic cigarettes comprising a casing made of plastic material inside which a quantity of powdered tobacco is contained; the machine is provided with a drum which receives an orderly mass of empty casings, and feeds them to a filling station in which a quantity of powdered tobacco is inserted into each empty casing and a filling unit which is arranged in correspondence to the filling station for feeding a quantity of powdered tobacco inside each empty casing from above; the filling unit is provided with a first hopper for the collection of powdered tobacco and a plurality of discs among which a first disc defining a bottom wall of the first hopper; wherein, between the first disc and a second disc a plurality of compartments is defined, each designed to contain the quantity of powdered tobacco to be inserted into a respective casing from above; and wherein the first disc and the second disc are mobile relative to one another, so as to vary the volume of the compartments and the quantity of powdered tobacco contained inside them.