The invention provides a vacuum attachment device for contact lithography of a flexible film substrate, comprising a vacuum pump, a frame, a flapper valve, a support table limiter, a vacuum chamber, amask support table, a bleed valve, a vacuum gauge, a top pressure mechanism, a sealing door opening/closing mechanism, a sealing door, a film holder, a flexible film, a sealing pad, and a photolithography mask. Wherein the mask support table can carry the photolithography mask and the film to be attached to move into and out of the vacuum chamber, the lithography mask is separated from that flexible film and spaced apart with the sealing pad, the support table limiter realizes positioning of the mask support table, the sealing door is closed, the vacuum pump and vacuum gauge control the degree of vacuum, As that action of the top pressure mechanism lowers the film support, the flexible film is in close contact with the sealing pad on the surface of the mask plate to form an airtight space, the pressure difference introduce by the vacuum is broken outside the airtight space by the bleed valve, the airtight space is compressed, the flexible film is closely adhered to the surface of themask plate, the mask support table is taken out and the mask plate and the flexible film are treated as a whole to be exposed.