A coupling mechanism for a tilting pad bearing, which couples a pad and a support in such a manner that the pad can be tilted with respect to the support, and comprises a first ball portion and a first socket portion to which a preload is applied, a contact surface between the first ball portion and the first socket portion serving as a first sliding spherical surface, the coupling mechanism further comprising a second ball portion and a second socket portion that come into contact with each other on a contact surface serving as a second sliding spherical surface, wherein a center of curvature of the first sliding spherical surface coincides with a center of curvature of the second sliding spherical surface, and the center of curvature exists between the first and second sliding spherical surfaces and a sliding surface of the pad, or on an opposite side across the sliding surface as viewed from the first and second sliding spherical surfaces, the coupling mechanism further comprising a shaft penetrating the first sliding spherical surface and the second sliding spherical surface, the second ball portion being fixed to one end side of the shaft, and the other end side of the shaft being fixed to the support by being screwed, wherein the first ball portion and the second socket portion are fixed to the pad, the first socket portion is fixed to the support, and the second ball portion is fixed to the support via the shaft, and the other end side of the shaft has a screw portion, and the preload is adjusted by adjusting a position of the screw portion with respect to the support, whereby the second ball portion is pressed toward the second socket portion, the pressing force thus applied to the second socket portion being transmitted to the first ball portion to press the first ball portion against the first socket portion, so that the preload between the first ball portion and the first socket portion is secured. a contact surface between the first ball portion and the first socket portion serving as a first sliding spherical surface, the coupling mechanism further comprising a second ball portion and a second socket portion that come into contact with each other on a contact surface serving as a second sliding spherical surface, wherein a center of curvature of the first sliding spherical surface coincides with a center of curvature of the second sliding spherical surface, and the center of curvature exists between the first and second sliding spherical surfaces and a sliding surface of the pad, or on an opposite side across the sliding surface as viewed from the first and second sliding spherical surfaces, the coupling mechanism further comprising a shaft penetrating the first sliding spherical surface and the second sliding spherical surface, the second ball portion being fixed to one end side of the shaft, and the other end side of the shaft being fixed to the support by being screwed, wherein the first ball portion and the second socket portion are fixed to the pad, the first socket portion is fixed to the support, and the second ball portion is fixed to the support via the shaft, and the other end side of the shaft has a screw portion, and the preload is adjusted by adjusting a position of the screw portion with respect to the support, whereby the second ball portion is pressed toward the second socket portion, the pressing force thus applied to the second socket portion being transmitted to the first ball portion to press the first ball portion against the first socket portion, so that the preload between the first ball portion and the first socket portion is secured.