because the inner or outer ring of the cross roller bearing has a two-part structure, the bearing gap can be adjusted, and even if a preload is applied, a high-precision rotary motion can be obtained. Moreover, due to its special structure, it can be applied to the joints and rotating parts of industrial robots, rotary tables of machining centers, rotating parts of manipulators, precision rotary tables, medical equipments, measuring instruments, IC manufacturing machines, etc.