The invention relates to a mechanical stretching device with a lifting function. The device comprises a left component, a right component and a lifting base. The left component and the right componentare both provided with same installation side plates, riveting side plates, front middle shared connecting rods, rear middle shared connecting rods, lifting connecting rods, connecting rotating sheets, connecting pieces, connecting sliding rods, rotating sheets, rear installation lugs, front installation lugs, foot rods 1, foot rods 2, foot rods 3, foot rods 4, foot rods 5, foot rods 6, foot installation plates, backrest connecting rods and backrest connecting pieces. The leg par adopts a three-section connection mode, all the connecting parts are limited respectively, so that the device hashigher stability, the foot structure can be contracted more completely by adopting three-section connection, the overall occupied volume of the seat is reduced, the product is convenient to store andtransport, the contact area between the bottom of the device and the ground is increased, and the stability of the whole device is improved.