STEERING DEVICE

A fastening mechanism fastens a first side plate to a second side plate by a first fastening member 32. A boss 50 with a rhombic cross-section of the first fastening member 32 is inserted into a telescopic-adjust long groove 23 of the second side plate. An outer periphery 50a of the boss 50 includes a first corner part 61 and a third corner part 63 each forming an obtuse angle and facing each other. The first corner part 61 is disposed on an upper side XU in an axial direction X, on a lower side YL in a tilt direction Y, while the third corner part 63 is disposed on a lower side XL in the axial direction X, on an upper side YU in the tilt direction Y. A width DT across the first corner part 61 and the third corner part 63 is shorter than a groove width W of the telescopic-adjust long groove 23.