A disk driving apparatus solves such problems that the position of a rotor is unstable and likely to float, and the rotor is displaced when an excessive acceleration is applied thereto, so that a hydrodynamic bearing mechanism can be used. This apparatus uses a single surface opposing type mechanism in a thrust bearing of a motor. It has a device using a magnetic attraction force to stabilize the position of the rotor and various devices for limiting the amount of movement of the rotor, in which devices members which physically contact the rotor and lock in are provided. As a result, a thrust bearing mechanism can be formed by use of a single surface opposing type thrust bearing which is simple in construction. Advantages such as low height, simplicity in construction, low price, or low consumption of power can be obtained. In particular, the feature of low height is extremely advantageous when a hydrodynamic bearing is used in a thin type apparatus.