The object is to keep the system safety even if the disk tray of the disk device is drawn out from the PC main body and led to a structurally dangerous state, and to prevent the disk tray from wrong operation beforehand. In addition, in a recording and playback system for recording and reproducing information on a recording medium such as optical disk, the guide shaft is biased by a bias means that can strongly apply power which doesn't degenerate, in order to improve the mounting stability, and in addition, to prevent the structural thickness of the entire unit from growing. A disk device composed to execute a load/unload a recording medium by making a disk tray advance and retreat in a chassis case, wherein a first detection switch 5 and a second detection switch 6 for detecting the load of the disk tray 1 are arranged in a way to be on different levels in respect to the operating direction thereof, or they are arranged on a wiring board packaged in the disk tray. Also, a recording and playback system, comprising a head unit composed to record and playback of an information by moving in parallel to the recording face of a recording medium; a guide shafts 10·13 for guiding the translation of the head unit; a bias means for applying bias force to the guide shaft all times; and a retaining means for adjusting the height position of the guide shaft by a drag balanced with the bias force of the bias means, wherein the bias means is composed by inserting a coil parts 22a·23a·24a of a helical torsion springs 22·23·24 into the guide shafts 10·13.