To provide a linear motion guide unit which is small, compact and short, and has a cylindrical body with a return path fitted into a fitting hole formed in a casing, and allows smooth rolling of rolling elements in the return path.

The cylindrical body 7 having a return path 20 is fitted into a fitting hole 8 with clearances 39, 40 in the casing 3. The cylindrical body 7 includes a both-end supporting beam section 25 and a cantilever beam section 26, which are opposed to each other in the longitudinal direction. The both-end supporting beam section 25 and cantilever beam section 26 are elastically deformably configured by receiving a pressing force from a roller 10 of the rolling elements which run on the return path 20. The both-end supporting beam section 25 is supported by an end support section 32 located at both ends of the cylindrical body 7 and formed around the periphery of the cylindrical body 7. One end of the cantilever beam section 26 is supported by a central supporting section 27 at the center of the cylindrical body 7, and the other end is formed as a free end.