PURPOSE: To improve cleaning capacity by a method wherein a bottom part of a base plate is raised up in the middle over a longitudinal direction and slanted downward toward the middle in a side view, so that a base plate bottom surface is provided with a large setting surface pressure by a normal operative force to wipe out any dirts from a slight one to a relatively obstinate one.

CONSTITUTION: A base plate 10 is an aluminum extruded form and its bottom part 10a is raised up in the middle so that a plurality of ribs 11 over a longitudinal direction rise up in the middle in a cross section, and further the whole of a bottom surface formed by a line which connects lower end surfaces of the ribs 11 is slanted downward toward the middle in a side view. A clamp 5 for mounting a cloth 4 is provided on both the right and left sides on an upper surface of the base plate 10. When a pushing operation forward of the base plate 10 is done with a long handle, only a front surface side forward of the raised middle is brought into contact with a floor surface, and when the base plate 10 is pulled rearward, the rear surface side is brought into contact with the floor surface. Accordingly, even if an operation is done by a conventional operative force, a surface pressure effecting on the floor surface becomes larger because a contact area is smaller, increasing rubbing force cleaning capacity.