In a disk device, having disks 2 and a hub 4 for holding thereof, to be attached onto a shaft 5 of a spindle motor, for rotary drive thereof, a groove 42 is formed on a bottom surface of a flange portion 41 of the hub 4, for receiving therein. A balance weight 8 to be received in this groove 42 has elasticity and an outer configuration of about "C", and further, in a portion thereof is attached at least one (1) piece of an auxiliary weight or more, thereby achieving unbalance correction at high accuracy with an aid of the balance weight. After being attached with one (1) piece or more of the "U" shaped auxiliary weight(s) directing it/them from an inner periphery to an outer periphery thereof, the "C" shaped balance weight is inserted or fitted into, while being suppressed a little bit in an inside thereof. Therefore, a disk device and the unbalance correcting method for that, can be obtained, in which spaces necessary for attaching and detaching are less, but enabling the balance correction at high accuracy.