A disk apparatus in which the thickness is suppressed. A recording/reproducing medium containing a disk rotatably in a hard case is moved substantially in a horizontal direction through an opening of the base of the disk apparatus for insertion and ejection operations of the recording/reproducing medium and recording/reproducing operation. For this purpose, the following are provided: a recording/reproducing unit for performing recording and reproduction, a container for containing the recording/reproducing medium at a predetermined position in the disk apparatus when the disk is inserted, a rotation motor for giving a predetermined turning effort by performing the chucking to the recording/reproducing medium, a chucking position where the chucking is performed, a vertical movement mechanism for moving the rotation motor to the waiting position where the recording/reproducing medium is inserted or ejected, a control mechanism for retaining the vertical movement mechanism to the chucking position, and a release mechanism for releasing and ejecting the recording/reproducing medium.