The invention relates to a method of using a flotation machine that is used in metallurgical processes and to a flotation machine. The flotation machine foams hydrophobic particles from an aqueous slurry that contains these particles. The flotation machine includes a flotation cell (1), and a rotor (2) that is inside the flotation cell. The rotor (2) is rotated at a mixing power, which maintains the suspension in the slurry and mixing of air with the slurry to form the foam, and the mixing power is controlled by adjusting the rotation speed of the rotor. The amount of solid matter S accumulated on the bottom of the cell (1) is determined, and the rotation speed of the rotor (2) is adjusted on the basis of the determined amount of solid matter. The flotation machine includes a measuring device (5) for determining the amount of solid matter accumulated on the bottom of the cell. The adjusting device (4) is arranged to adjust the rotation speed of the motor (3), which rotates the rotor (2), on the basis of the measuring result of the measuring device (5) to remove the solid matter from the bottom of the cell.