A disk storage medium processing apparatus includes a disk conveying device for conveying a disk between a disk loading/unloading slot of an apparatus body and a centering position of a traverse unit. The disk conveying device includes a pair of first and second disk guide arms which are pivotably disposed on the apparatus body and which can hold the periphery of the disk to convey the disk. Therefore, the disk storage medium processing apparatus can easily and flexibly conduct the control for conveyance of the disk no matter whether the disk has a small diameter or a large diameter, with keeping protection of the recording surface of the disk and can be formed more compactly.