A steering device comprising: a steering shaft that is rotatably and axially supported by a column (3, 4) and is attachable to a steering wheel toward a vehicle body rear; a steering lock apparatus (6, 6A) that is attached to the column (3, 4) and allows a lock pin operated by an ignition key operation to engage with the steering shaft and lock the steering shaft; a flange section that is formed integrally with the column (3, 4) so as to protrude from an outer periphery of the column (3, 4) outward along a radial direction and includes a mounting surface for mounting a housing (61, 61A) for encasing the steering lock apparatus (6, 6A); where the steering device comprises: a slant plane that is formed on the flange section opposite the mounting surface and is shaped so as to gradually increase a flange section thickness along a direction orthogonal to an axial direction of the column (3, 4) from outside along the radial direction to the outer periphery of the column; a bolt that fastens the housing (61, 61A) for encasing the steering lock apparatus (6, 6A) to the mounting surface of the flange section; a counterbore that is formed in the flange section, toward the slant plane, and is deep such that a top end of the bolt head section is below the slant plane; characterised by a rib (47, 48) formed protrusively from the mounting surface of the flange section near the steering lock apparatus (6, 6A) so as to cover a tightening surface of the steering lock apparatus (6, 6A) attached to the flange section. a steering shaft that is rotatably and axially supported by a column (3, 4) and is attachable to a steering wheel toward a vehicle body rear; a steering lock apparatus (6, 6A) that is attached to the column (3, 4) and allows a lock pin operated by an ignition key operation to engage with the steering shaft and lock the steering shaft; a flange section that is formed integrally with the column (3, 4) so as to protrude from an outer periphery of the column (3, 4) outward along a radial direction and includes a mounting surface for mounting a housing (61, 61A) for encasing the steering lock apparatus (6, 6A); where the steering device comprises: a slant plane that is formed on the flange section opposite the mounting surface and is shaped so as to gradually increase a flange section thickness along a direction orthogonal to an axial direction of the column (3, 4) from outside along the radial direction to the outer periphery of the column; a bolt that fastens the housing (61, 61A) for encasing the steering lock apparatus (6, 6A) to the mounting surface of the flange section; a counterbore that is formed in the flange section, toward the slant plane, and is deep such that a top end of the bolt head section is below the slant plane; characterised by a rib (47, 48) formed protrusively from the mounting surface of the flange section near the steering lock apparatus (6, 6A) so as to cover a tightening surface of the steering lock apparatus (6, 6A) attached to the flange section. a slant plane that is formed on the flange section opposite the mounting surface and is shaped so as to gradually increase a flange section thickness along a direction orthogonal to an axial direction of the column (3, 4) from outside along the radial direction to the outer periphery of the column; a bolt that fastens the housing (61, 61A) for encasing the steering lock apparatus (6, 6A) to the mounting surface of the flange section; a counterbore that is formed in the flange section, toward the slant plane, and is deep such that a top end of the bolt head section is below the slant plane; characterised by a rib (47, 48) formed protrusively from the mounting surface of the flange section near the steering lock apparatus (6, 6A) so as to cover a tightening surface of the steering lock apparatus (6, 6A) attached to the flange section.