Abstract: The invention relates to a flotation machine used for separating valuable ingredients, such as metal concentrates, from the rest of the material, which flotation machine comprises at least means for feeding slurry to be treated in the flotation cell into said flotation cell, means for agitating the slurry by a rotor which is to be rotated by a rotation device installed in the vertical direction of the flotation cell underneath the rotor, means for feeding air into the slurry, means for removing the material flotated in the flotation cell and means for removing material that is left non-flotated in the flotation cell. According to the invention the shaft (11, 28) of the rotor (10, 26) meant for agitating the slurry (3, 23) and for feeding air into the slurry (3, 23) and of the rotation device (12, 27) is sealed in the flotation cell (1, 21) by a mechanical sealing member (15).