A bonding apparatus has an upper chuck and a lower chuck for holding wafers. The upper chuck is configured such that the center portion is bent to be convex when pressurized with a predetermined pressure. On the bottom surface of the lower chuck, there is an insulating ring formed of a combination of a plurality of insulating members to support the periphery of the lower chuck. The bottom surface of the insulating ring is supported by a support ring formed of a combination of a plurality of supporting members. The supporting members and the lower chuck are fixed by a bolt provided for each of the supporting members. The bolt is inserted through a through hole and a through hole which are formed in the insulating members and the supporting members, respectively, the through holes having a diameter larger than a diameter of the bolt.