Abstract: An apparatus for wet cleaning floor or wall surfaces comprises one or more cylindrical brushes which may be rotated by a motor so that they are throwing liquid and dirt from the floor or wall surface on to a rotating cylinder or a moving endless belt. Liquid and dirt is continuously removed from the outer peripheral surface of the cylinder or belt by means of a suction nozzle extending along the axial length of the cylinder and immediately adjacent to the peripheral surface thereof. The suction nozzle may have a lower edge functioning as a scraping member which is in contact with the peripheral surface of a cylinder. Liquid and dirt removed from the cylinder by means of the suction nozzle is passed to a container for collecting dirty liquid.