Abstract: An auto-balancing disk drive apparatus is disclosed which makes it possible to decrease the installation space of an auto balancing unit thereof which is capable of automatically preventing an up and down movement of a disk when the disk is rotated at a high speed, reducing the driving force which is needed for the rotation of the disk and auto balancing unit, and reducing the noise and vibration which occur at the auto balancing unit. The disk drive apparatus includes a motor generating a rotational force with respect to a rotary shaft, and an auto balancing unit installed radially laterally and co-planar with respect to the rotary shaft for automatically correcting an unbalanced state of a rotation member when an unbalanced state occurs at the rotation member.