A first shaft and a second shaft are rotatably supported by a casing in a mutually parallel but offset manner, and an intermediate member is interposed between mutually opposing axial ends of these shafts. The intermediate member transmits torque from the first shaft to the second shaft, but the intermediate member is radially slidable relative to the first shaft and is engaged with a radially offset point of the second shaft. Because the distance between the axial center line of the first shaft and the point of engagement between the intermediate member and the second shaft changes with the angular displacement of the first shaft, a desired nonlinear property can be accomplished between the angular displacements of the first shaft and the second shaft. This property can be used for achieving a desired variable gear ratio suitable for the steering device. Further, the mutual sliding movement between the first shaft and the intermediate shaft in the radial direction accommodates such a relationship, and it can be achieved in a dimensionally accurate and play free manner because the movements of the moveable members strictly consist of rotational movements of circular members and simple linear movements. Roller bearings and ball bearings should be used in various parts to minimize plays.