PURPOSE: To provide an excellent thin spindle motor in which rotor frame also serves as a clamp magnet yoke.

CONSTITUTION: A rotor frame 12 pressed from a magnetic material is press fit to a rotor shaft 1. A ring type protrusion 12a is provided on the plane part at the outside of the rotor frame 12 while a clamp magnet disc 14 is disposed on the inside of the protrusion 12a and a ring type spindle hub 13 is fixed to the outside of the protrusion 12a. Since the rotor frame 12 also serves as a clamp magnet yoke, an excellent spindle motor which is made thin by an amount corresponding to the board thickness of the clamp magnet yoke can be obtained.