To provide a rack bush capable of obtaining a good steering feeling.

The rack bush 1 has a bellows cylindrical shape body 4 having an outer periphery 4a and an inner periphery 4b. The rack bush further has valleys 51, 52, 53 and valleys 61 62 alternately arranged in the outer periphery 4a in an axial direction X1. The rack bush has mountain parts 71, 72, 73 and valleys 81, 82, 83 alternately arranged in the inner periphery 4b in the axial direction X1. Mounting parts 71, 72, 73 are arranged in the back side of the valleys 51, 52, 53. A first inner diameter d1 of the top 72a of the first mountain part 72 is lesser than the outer diameter D of a rack shaft 3 in an unloaded condition. The second inner diameter d2 of the tops 71a. 73a of the second mountain part 71, 73 is larger than the first inner diameter d1 (d2>d1).