An air file has a body, a fastening member, and a driving assembly. The body has a handle and a front cover connected to the handle. The fastening member is swingably assembled to the front cover and has a pivoting end and a connecting end. The pivoting end of the fastening member is inserted inside the front cover. The connecting end of the fastening member extends out of the front cover. The driving assembly is mounted inside the body and has an eccentric shaft and a swinging unit. The eccentric shaft is connected to a driving device and has an eccentric hole facing to the front cover. The swinging unit has a pivoting portion and a ball joint. The pivoting portion is pivotally connected to the pivoting end of the fastening member. The ball joint is engaged in the eccentric hole of the eccentric shaft.