plane at a predetermined speed the spin chuck 10 holds the semiconductor wafer w in such a state that the surface of the semiconductor wafer w to be cleaned is facing upward a vertical support shaft 12 is disposed adjacent to the spin chuck 10 and supports at an upper end thereof a swing arm 14 extending horizontally the support shaft 12 is vertically movable and rotatable about its own axis a substantially cylindrical housing 16 is supported by the forward end of the swing arm 14 as shown in fig2 a bearing retaining member 17 is disposed in the housing 16 for retaining bearings 17 a and 17 b a rotating shaft 18 extending vertically is rotatably supported by the bearings 17 a and 17 b a driven bevel gear 20 a is mounted on the top end of the rotating shaft 18 a bearing casing 23 is mounted on the upper portion of the bearing retaining member 17 for housing bearings 23 a and 23 b a drive shaft 22 extending horizontally is rotatably supported by the bearings 23 a and 23 b a drive bevel gear 20 b which engages with the driven bevel gear 20 a is mounted on the forward end of the drive shaft 22 the drive shaft 22 is coupled to a drive source not shown such as a motor provided in the.