POLISHING DEVICE

PURPOSE:To increase the flowing speed of coolant flowing a coolant passage and to flow coolant smoothly and surely, in the case of a lower surface plate being rotated, by providing a coolant flowing-in port at the position higher than a coolant feeding outlet port. CONSTITUTION:A lot of coolant passages 23 which curve in the rotation direction of a lower surface plate 10 as facing to the external part in the radial direction of a lower surface place 10 are formed in the lower surface plate 10. The two adjacent coolant passages 23 in these coolant passages are communicated by the outer edge part of the lower surface plate 10 and also a coolant flow-in port 26 is formed at the center side of the lower surface plate 10 of the other part in the adjacent two coolant passages 23. Moreover, a coolant feeding-out port 27 is formed, at the center side of the lower surface plate 10, of the other part in adjacent two coolant passages 23 and on the other hand the coolant flow-in port 26 is provided at the position higher than the coolant feeding out port 27. Thus, the flowing speed of coolant flowing the coolant passage 23 in increased, in the case of the lower surface plate 10 being rotated and cooling efficiency of the lower surface plate 10 can be improved.