A disk drive device is arranged so as to swing a traversing mechanism which has an optical pickup and a spindle motor mounted thereon. In a shift mechanism of the optical pickup, its outer end in the radial direction of the optical disk is provided to extend beyond a periphery of the optical disk, and in loading, the optical pickup is caused to withdraw to the outer end which is provided to extend. Therefore, as to the optical pickup which is thicker than the spindle motor and determines the thickness of the whole device, the amount of swing of the pickup is decreased while reliably avoiding the contact between the pickup and the optical disk, thus realizing the reduction in thickness of the device. As a result, it is possible to realize front loading of the optical disk at low cost.