A wheel speed detecting device comprising: a wheel hub that supports an axle, a brake disc being secured to the wheel hub; a pulsar ring secured to the wheel hub; and a magnetic sensor configured to detect a passing of a detected portion disposed on the pulsar ring, wherein the wheel hub forms a cylindrical outer peripheral surface as an outer peripheral side spigot portion, the brake disc includes a disc-side spigot portion in contact with the cylindrical outer peripheral surface, the pulsar ring includes a ring-side spigot portion in contact with the cylindrical outer peripheral surface, and the brake disc and the pulsar ring are co-clamped and secured to a mounting portion formed at the wheel hub with a plurality of fastening members, wherein a plurality of extension stays are formed on the pulsar ring, the extension stays extending outside in a radial direction with respect to the detected portion and then bending in a peripheral direction, and ring-side through-holes and the ring-side spigot portion are formed at the extension stays, the fastening members passing through the ring-side through-holes, wherein, in a radial direction, the cylindrical outer peripheral surface is positioned between an opening for the axle to pass through and hub-side through-holes, the hub-side through-holes being formed at the mounting portions for the fastening members to pass through, and the ring-side spigot portion is disposed at a position separated outside in a radial direction from an outer peripheral section of the pulsar ring, wherein the pulsar ring and the brake disc are mounted to the mounting portion in this order, the extension stays include crank-shaped bent portions, the bent portions displacing the ring-side spigot portion in an axial direction, and when the pulsar ring and the brake disc are co-clamped to the mounting portion, an outer surface of the pulsar ring in an axial direction is positioned outside with respect to an outer surface of the brake disc in an axial direction. a wheel hub that supports an axle, a brake disc being secured to the wheel hub; a pulsar ring secured to the wheel hub; and a magnetic sensor configured to detect a passing of a detected portion disposed on the pulsar ring, wherein the wheel hub forms a cylindrical outer peripheral surface as an outer peripheral side spigot portion, the brake disc includes a disc-side spigot portion in contact with the cylindrical outer peripheral surface, the pulsar ring includes a ring-side spigot portion in contact with the cylindrical outer peripheral surface, and the brake disc and the pulsar ring are co-clamped and secured to a mounting portion formed at the wheel hub with a plurality of fastening members, wherein a plurality of extension stays are formed on the pulsar ring, the extension stays extending outside in a radial direction with respect to the detected portion and then bending in a peripheral direction, and ring-side through-holes and the ring-side spigot portion are formed at the extension stays, the fastening members passing through the ring-side through-holes, wherein, in a radial direction, the cylindrical outer peripheral surface is positioned between an opening for the axle to pass through and hub-side through-holes, the hub-side through-holes being formed at the mounting portions for the fastening members to pass through, and the ring-side spigot portion is disposed at a position separated outside in a radial direction from an outer peripheral section of the pulsar ring, wherein the pulsar ring and the brake disc are mounted to the mounting portion in this order, the extension stays include crank-shaped bent portions, the bent portions displacing the ring-side spigot portion in an axial direction, and when the pulsar ring and the brake disc are co-clamped to the mounting portion, an outer surface of the pulsar ring in an axial direction is positioned outside with respect to an outer surface of the brake disc in an axial direction.