To prevent a chuck table from being curved due to temperature change, its sucking holding part from cracking, and the sucking holding part from being separated from the frame body even if the chuck table becomes larger in diameter because wafers become larger in diameter.

The sucking holding part 21 composing the chuck table 20 is formed with a porous ceramic consisting mainly of zirconia having almost the same coefficient of linear expansion of 9.010-6/C as the coefficient of linear expansion, 10.410-6/C, of the stainless that forms the frame body 22. This solves the problems that the chuck table 20 curves by the temperature changes, the cracks are generated in the sucking holding part 21 and the sucking holding part 21 separates from the frame body 22, and restrains the accuracy of the upper surface of the chuck table 20 from deteriorating, even if the temperature changes when the chuck table becomes larger in diameter because the wafers become larger in diameter, thus to machine the wafers with high accuracy.