In a steering device having a steering lock device, stress applied to a base portion of a flange section is reduced. Relief portions have round corners formed where the relief portions meet the outer periphery of the outer column, respectively. With the relief portions concave by β3 from the mounting surface, radius R1 of each of the round corners of the relief portions can be made larger than radius R2 of a round corner of the mounting surface. This makes it possible to avoid interference between the relief portions and the corner at an inner end, in the vehicle width direction, of the right clamping surface of the steering lock device.