A steering device comprising: a steering column including an outer column and an inner column, a part of the inner column being enclosed by the outer column; a support bracket attachable to a vehicle body to support the steering column; and a tightening mechanism including an adjusting rod, and having a first state in which the steering column is tightened with the support bracket and a second state in which the tightening is released, characterized in that the outer column includes: a first surface (49a, 49c) and a second surface (49b, 49d) arranged spaced apart from each other in a first direction, which intersects an axial direction, and such that the first surface (49a, 49c) and the second surface (49b, 49d) are pressed by the support bracket in the first state; a clamp part (38, 38a) having a third surface, the third surface being provided independently from the first surface (49a, 49c) and the second surface (49b, 49d), and such that the third surface is pressed by the support bracket in the first state; and a slit provided between the first surface (49a, 49c) and the second surface (49b, 49d) in the first direction, the slit includes: a first slit extending in at least the axial direction; and a second slit (37a, 37b, 37c, 37d) provided to be continuous with the first slit and extending in a direction which intersects the first slit, the adjusting rod is inserted through the first slit, and the third surface is arranged between the first surface (49a, 49c) and the second surface (49b, 49d) in the first direction. a steering column including an outer column and an inner column, a part of the inner column being enclosed by the outer column; a support bracket attachable to a vehicle body to support the steering column; and a tightening mechanism including an adjusting rod, and having a first state in which the steering column is tightened with the support bracket and a second state in which the tightening is released, characterized in that the outer column includes: a first surface (49a, 49c) and a second surface (49b, 49d) arranged spaced apart from each other in a first direction, which intersects an axial direction, and such that the first surface (49a, 49c) and the second surface (49b, 49d) are pressed by the support bracket in the first state; a clamp part (38, 38a) having a third surface, the third surface being provided independently from the first surface (49a, 49c) and the second surface (49b, 49d), and such that the third surface is pressed by the support bracket in the first state; and a slit provided between the first surface (49a, 49c) and the second surface (49b, 49d) in the first direction, a first surface (49a, 49c) and a second surface (49b, 49d) arranged spaced apart from each other in a first direction, which intersects an axial direction, and such that the first surface (49a, 49c) and the second surface (49b, 49d) are pressed by the support bracket in the first state; a clamp part (38, 38a) having a third surface, the third surface being provided independently from the first surface (49a, 49c) and the second surface (49b, 49d), and such that the third surface is pressed by the support bracket in the first state; and a slit provided between the first surface (49a, 49c) and the second surface (49b, 49d) in the first direction, the slit includes: a first slit extending in at least the axial direction; and a second slit (37a, 37b, 37c, 37d) provided to be continuous with the first slit and extending in a direction which intersects the first slit, the adjusting rod is inserted through the first slit, and the third surface is arranged between the first surface (49a, 49c) and the second surface (49b, 49d) in the first direction. a first slit extending in at least the axial direction; and a second slit (37a, 37b, 37c, 37d) provided to be continuous with the first slit and extending in a direction which intersects the first slit,