An angle-adjustable rehabilitation device includes first and second racks between two lateral covers, a locking unit of the second rack is capable of switching the first rack between an adjustable position and a nonadjustable position. When in the adjustable position, the rotatable angle of the first rack can be freely adjusted. The control members of the two angle-adjustment positioning members protrude out of the two lateral covers, therefore, angle adjustment can be easily done without removing any components. Furthermore, the arc-shaped angle scale on the two lateral covers makes the angle adjustment more readable and controllable, and the first rack can be moved back into the non-adjustable position automatically after angle adjustment is done.