PURPOSE: A spindle motor is provided to easily mount a disc on a chuck due to an installation force which becomes weak by forming a space portion between the chuck and a rotor. CONSTITUTION: A rotator (10) comprises a shaft (11), a rotor case (12), and a main magnet (13). A chuck (20) comprises a chuck base (21) and a clamp. A stator (30) supports the shaft rotatably. An armature (40) is equipped in the stator. A core of the armature generates an electromechanical power with the main magnet. A space portion (22) is formed between 'a lower side of an inside diameter of the chuck base' and the rotor.
