A tray-type structure device includes a side plate, a front plate attached to a forward end of the side plate, having the functions of opening and closing, and positioned on the front side of a housing, a top plate attached to an upper end of the side plate, with a plurality of openings formed therein, and having the function of variably setting a ventilation resistance, a bottom plate attached to a lower end of the side plate, with a plurality of openings formed therein, and having the function of variably setting a ventilation resistance, and a back plate attached to a rearward end of the side plate, having the functions of opening and closing, and positioned on a side of the housing toward a backboard. The device has a tray structure having a tray-like shape formed by the front plate, top plate, bottom plate, side plate and back plate.