An apparatus correctly measures motion characteristics a head gimbal assembly exhibits when turned in a radial direction of a hard disk. The apparatus includes an assembly support to fixedly support the head gimbal assembly on a center axis that corresponds to a rotation axis around which the head gimbal assembly is turned in actual use, a disk drive to rotatably support the hard disk and turn around a turn axis that is concentric with the center axis on which the head gimbal assembly is fixedly supported, and a turn unit to turn the disk drive around the turn axis, thereby creating a relative turn of the head gimbal assembly with respect to the hard disk.