The present invention provides a disc tray shift device including a disc tray having at least one disc placement portion, a rack having an arc portion and at least one straight portion, the rack being arranged on the disc tray, and a sun gear, a planet gear which has a large-tooth-portion engaged with the sun gear and a small-tooth-portion engaged with the rack, and a shift mechanism for shifting the disc tray between a position where the disc placement portion is withdrawn externally and a position where the disc placement portion is housed internally, wherein teeth of at least one of the sun gear, the planet gear, and the rack are profile-shifted.