The invention discloses a cover plate folding and opening type mechanical attic device and belongs to the field of building attics. By means of the mechanical attic device, an attic cover plate is designed to be of a horizontal curtain-shaped cover plate structure, a cover plate can be controlled to be folded when the attic is not used, the ventilating performance of the whole space is maintained,and the lighting performance of small-area buildings is ensured; meanwhile, a folding stair linked with the folding or unfolding action of the cover plate is further arranged on the mechanical atticdevice, the folding stair is driven to be synchronously unfolded through a linking control frame while the attic cover plate is unfolded, people can enter and exit from the attic conveniently, when the attic cover plate is folded, the stair can automatically reset, and space is not occupied; and in addition, a folding handrail is further arranged, the folding or unfolding action of the folding handrail and the attic cover plate is also of linking design, the linking control frame is used for driving the folding handrail to ascend to be unfolded, the use safety of the attic is improved, when the attic cover plate is folded, the folding handrail can automatically descend to be folded, and the light shielding rate of the handrail is reduced.