The present invention relates to a balance structure of a fan, which comprises a hub and a balance slider. The hub has a circumferential portion and a top portion. The circumferential portion has a plurality of blades. The top portion is provided with a groove having a latch portion. The balance slider has a receiving portion slidingly engaging with the latch portion such that the balance slider can be slidingly disposed in the groove and the balance slider can move to a balance position automatically during the rotation of the hub. In this way, the effect of automatic balance can be achieved.