A bookbinding apparatus for bookbinding such that a cover sheet forms a front and a back cover by bonding the cover sheet and a spine portion of a bundle (Sa) of sheets together, the bookbinding apparatus comprising: a sheet bundle holding unit for holding the bundle of sheets; a cover-sheet outfitting device for holding and conveying the cover sheet to a cover sheet bonding position where the cover sheet is bonded to the bundle of sheets; a cover sheet supply device for housing and supplying the cover sheet to the cover sheet outfitting device; a cover-sheet trimming device which trims the cover sheet conveyed from the cover-sheet outfitting device, to a predetermined length prior to bonding the cover sheet to the bundle of sheets; the cover sheet outfitting device including an alignment device for positioning the cover sheet, a movable casing and a transporting member (81, 82) supported by the movable casing for transporting the cover sheet to a prescribed position on the cover sheet outfitting device, the movable casing being driven by an elevation device to move the moveable casing up and down vertically such that the cover-sheet outfitting device receives the cover sheet transported from the cover-sheet supply device at a lowered position and comes to a bonding position where the cover-sheet outfitting device bonds the cover sheet at a raised position; wherein the alignment device includes alignment plates (91A, 91B) movable, under control of a motor coupled to the alignment plates, in the width direction of the cover sheet to align the cover sheet by regulating an end side of the cover sheet parallel to a direction of transportation conducted by the transporting member; and wherein the cover sheet trimming device comprises a cutter unit (71, 72) including a knife supported by a moving member slidable in a linear movement from an initial position to cut the cover sheet in the width direction of the cover sheet, the cover-sheet outfitting device being integrally formed with the cover-sheet trimming device so that the cover-sheet outfitting device can be raised and lowered together with the cover-sheet trimming device. a sheet bundle holding unit for holding the bundle of sheets; a cover-sheet outfitting device for holding and conveying the cover sheet to a cover sheet bonding position where the cover sheet is bonded to the bundle of sheets; a cover sheet supply device for housing and supplying the cover sheet to the cover sheet outfitting device; a cover-sheet trimming device which trims the cover sheet conveyed from the cover-sheet outfitting device, to a predetermined length prior to bonding the cover sheet to the bundle of sheets; the cover sheet outfitting device including an alignment device for positioning the cover sheet, a movable casing and a transporting member (81, 82) supported by the movable casing for transporting the cover sheet to a prescribed position on the cover sheet outfitting device, the movable casing being driven by an elevation device to move the moveable casing up and down vertically such that the cover-sheet outfitting device receives the cover sheet transported from the cover-sheet supply device at a lowered position and comes to a bonding position where the cover-sheet outfitting device bonds the cover sheet at a raised position; wherein the alignment device includes alignment plates (91A, 91B) movable, under control of a motor coupled to the alignment plates, in the width direction of the cover sheet to align the cover sheet by regulating an end side of the cover sheet parallel to a direction of transportation conducted by the transporting member; and wherein the cover sheet trimming device comprises a cutter unit (71, 72) including a knife supported by a moving member slidable in a linear movement from an initial position to cut the cover sheet in the width direction of the cover sheet, the cover-sheet outfitting device being integrally formed with the cover-sheet trimming device so that the cover-sheet outfitting device can be raised and lowered together with the cover-sheet trimming device.