A disk drive apparatus includes a mainframe equipped with a disk table which is rotated by a spindle motor, a disk holder which is provided on the mainframe so as to be movable in the up and down directions and which is adapted to hold a cartridge of a floppy disk, and an eject plate which is provided on the mainframe so as to be movable in the forward and backward directions, wherein the disk holder is moved up or down in conjunction with the forward and backward movement of the eject plate. The disk holder up and down mechanism includes at least three pins provided on each of the side plates of the disk holder, and at least three guide portions which are provided on each of the side plates of the eject plate so as to correspond to the pins of the disk holder, respectively and which are adapted to be cooperatively associated with the corresponding pins, in which each of the guide portions is formed from either a first guide portion which has only a slanting cam surface which acts on the corresponding pin when the eject plate is moved from its first position to its second position, or a second guide portion which has only a slanting cam surface which acts on the corresponding pin when the eject plate is moved from its second position to its first position. If three pins are provided on each side plate of the disk holder, the corresponding side plate of the eject plate is formed with two first guide portions and one second guide portion positioned therebetween.