A steering device comprising: a column shaft that is configured to extend and retract in a first axis direction; a column jacket including a lower jacket and an upper jacket fitted to the lower jacket, the column jacket supporting the column shaft so that the column shaft is configured to rotate, the column jacket being configured to extend and retract in the first axis direction during telescoping adjustment; a fastening mechanism including a fastening shaft, the fastening shaft being supported by the lower jacket and being configured to rotate, the fastening shaft having a first flat portion on an outer peripheral surface of the fastening shaft, the first flat portion extending in a second axis direction, the second axis direction being an axis direction of the fastening shaft, the fastening mechanism being configured to cause the lower jacket to fasten and hold the upper jacket via the fastening shaft; a first tooth member that is configured to move integrally with the upper jacket in the first axis direction; a second tooth member that is supported by the lower jacket so that the second tooth member is configured to rotate, the second tooth member being configured to mesh with the first tooth member as the second tooth member rotates; an energizing member that is configured to elastically energize the second tooth member so that the second tooth member meshes with the first tooth member when the fastening mechanism fastens the upper jacket; and a release member, the release member including: a cylindrical portion that is fitted onto the fastening shaft, the cylindrical portion having a second flat portion that is formed on an inner peripheral surface of the cylindrical portion, the second flat portion facing the first flat portion so as to be configured to transmit torque; and a release portion that is provided on an outer peripheral surface of the cylindrical portion and is configured to engage with the second tooth member, wherein: when the release member is rotated along with rotation of the fastening shaft toward a fastening release side, the release member causes the release portion to be engaged with the second tooth member, and thus causes the second tooth member to rotate so as to be displaced to a non-meshed side against the energizing member; characterized in that: a projecting portion is formed on at least one of the first flat portion and the second flat portion, the projecting portion being elastically engaged with another one of the first flat portion and the second flat portion and restraining backlash between the first flat portion and the second flat portion. a column shaft that is configured to extend and retract in a first axis direction; a column jacket including a lower jacket and an upper jacket fitted to the lower jacket, the column jacket supporting the column shaft so that the column shaft is configured to rotate, the column jacket being configured to extend and retract in the first axis direction during telescoping adjustment; a fastening mechanism including a fastening shaft, the fastening shaft being supported by the lower jacket and being configured to rotate, the fastening shaft having a first flat portion on an outer peripheral surface of the fastening shaft, the first flat portion extending in a second axis direction, the second axis direction being an axis direction of the fastening shaft, the fastening mechanism being configured to cause the lower jacket to fasten and hold the upper jacket via the fastening shaft; a first tooth member that is configured to move integrally with the upper jacket in the first axis direction; a second tooth member that is supported by the lower jacket so that the second tooth member is configured to rotate, the second tooth member being configured to mesh with the first tooth member as the second tooth member rotates; an energizing member that is configured to elastically energize the second tooth member so that the second tooth member meshes with the first tooth member when the fastening mechanism fastens the upper jacket; and a release member, the release member including: a cylindrical portion that is fitted onto the fastening shaft, the cylindrical portion having a second flat portion that is formed on an inner peripheral surface of the cylindrical portion, the second flat portion facing the first flat portion so as to be configured to transmit torque; and a release portion that is provided on an outer peripheral surface of the cylindrical portion and is configured to engage with the second tooth member, wherein: a cylindrical portion that is fitted onto the fastening shaft, the cylindrical portion having a second flat portion that is formed on an inner peripheral surface of the cylindrical portion, the second flat portion facing the first flat portion so as to be configured to transmit torque; and a release portion that is provided on an outer peripheral surface of the cylindrical portion and is configured to engage with the second tooth member, wherein: when the release member is rotated along with rotation of the fastening shaft toward a fastening release side, the release member causes the release portion to be engaged with the second tooth member, and thus causes the second tooth member to rotate so as to be displaced to a non-meshed side against the energizing member; characterized in that: a projecting portion is formed on at least one of the first flat portion and the second flat portion, the projecting portion being elastically engaged with another one of the first flat portion and the second flat portion and restraining backlash between the first flat portion and the second flat portion.