PURPOSE: To obtain a washing device generating no deviation on the upper surface of a vacuum chuck by a method wherein the lower surface of a cup-like washing member, which is attached to the lower end of a rotating shaft, and the upper surface of the vacuum chuck of a plane-surfaced automatic grinder and the like are formed using the same material.

CONSTITUTION: The title washing device is interlocked with the driving shaft 3a of a motor 3 through a pair of gears 4a and 4b, and a cup-like washing member 5 is attached to the lower end of a rotating shaft 5a which is droopingly provided in a freely vertically moving and freely rotatable manner. The washing member 5 is lowered, it is brought into contact with the upper surface of the vacuum chuck B of an automatic surface grinder, and the ground semiconductor wafer is washed while it is being revolved and rotated. At this point, at least the lower surface of the washing member 5 and the upper surface of the vacuum chuck B are formed using the same material. Besides, at least the lower surface of the washing member 5 and the upper surface of the vacuum chuck B are formed using pure alumina respectively.