A slide device, comprising first class members having spaces opening to sides formed in the longitudinal directions thereof and second class rail members positioned in the spaces, wherein either of the first and second class rail members movable relative to each other are formed in movable rail members and the other are formed in fixed rail members, the movable rail members are installed at both side parts of slide plates, the slide plates are positioned on brackets parallel with each other, and the movable rail member installed on the slide plate is supported by the fixed rail member installed on the slide plate.