To provide a placing plate device capable of holding an OA device to be used on a desk by simply moving over the desk at the time of not using.

The device is formed of two opposed supporting frames 3, 3 integrally formed on a U-shaped fixed plate 1 fixed to the center of the back surface of a desk top plate A-1, two parallel arms 21, 22 whose one-side ends are pivoted by the side surface of the holding part 12 of the rear surface of a placing plate C and the other ends of which are pivoted to the side surfaces of the two opposed supporting frames 3, 3 integrally formed on the plate 1 fixed to the center of the rear surface of the plate A-1 to rotate with these pivoting parts as supporting points 25, 26, and a damper 30 whose one end is pivoted to a lower axis 4 between the two opposed frames 3, 3 and the other end of which are connected with the arm 22. Thus, the plate C is vertically moved by the rotation of the arms 21, 22 by the supporting points 25, 26 and the extension/contraction of the damper 30 with it.