A bookbinding apparatus for producing a booklet by coating an adhesive onto a back side of a bundle of sheets (Sa) and by pasting a book cover onto the back side of the bundle of sheets, comprising: a sheet conveyance path for conveying sheets; an oblique cutout portion forming section to form a cutout on an edge of each sheet of the bundle of sheets in such a way that an oblique cutout portion (Va) is formed along the width of the back side of the bundle of sheets, wherein the oblique cutout portion forming section comprises a cutting section (301, 302) to form a cutout on an edge of a sheet and a shifting section to shift one of a conveyed sheet and the cutting section in a sheet width direction perpendicular to a sheet conveying direction; a fixed cutout portion forming section; a sheet bundle accommodating section to accommodate the bundle of sheets on which the oblique cutout portion is formed; a coating section to coat an adhesive on the back side of the bundle of sheets accommodated in the sheet bundle accommodating section; a bookbinding section to paste a book cover on the adhesive-coated back side of the bundle of sheets so as to produce the booklet; and a control part to control the shifting section for: forming, by the oblique cutout portion forming section, the oblique cutout portion (Va) by shifting the one of a conveyed sheet and the cutting section in a sheet width direction perpendicular to a sheet conveying direction by a shift amount (Δ) such that a position of a cutout on a second sheet is shifted by the distance relative to a position of a cutout on a first sheet, and to repeat this shifting step for each sheet until the oblique cutout portion has been formed; and forming, by the fixed cutout portion forming section, a fixed cut-out part (Vd) fixedly arranged in the vicinity of both edge parts of the sheet width direction by not shifting the one of a conveyed sheet and the cutting section in the sheet width direction prior to forming cut-outs of the fixed cut-out part in each sheet, whereby the cut-outs of the fixed cut-out part are formed in the same position in each sheet. a sheet conveyance path for conveying sheets; an oblique cutout portion forming section to form a cutout on an edge of each sheet of the bundle of sheets in such a way that an oblique cutout portion (Va) is formed along the width of the back side of the bundle of sheets, wherein the oblique cutout portion forming section comprises a cutting section (301, 302) to form a cutout on an edge of a sheet and a shifting section to shift one of a conveyed sheet and the cutting section in a sheet width direction perpendicular to a sheet conveying direction; a fixed cutout portion forming section; a sheet bundle accommodating section to accommodate the bundle of sheets on which the oblique cutout portion is formed; a coating section to coat an adhesive on the back side of the bundle of sheets accommodated in the sheet bundle accommodating section; a bookbinding section to paste a book cover on the adhesive-coated back side of the bundle of sheets so as to produce the booklet; and a control part to control the shifting section for: forming, by the oblique cutout portion forming section, the oblique cutout portion (Va) by shifting the one of a conveyed sheet and the cutting section in a sheet width direction perpendicular to a sheet conveying direction by a shift amount (Δ) such that a position of a cutout on a second sheet is shifted by the distance relative to a position of a cutout on a first sheet, and to repeat this shifting step for each sheet until the oblique cutout portion has been formed; and forming, by the fixed cutout portion forming section, a fixed cut-out part (Vd) fixedly arranged in the vicinity of both edge parts of the sheet width direction by not shifting the one of a conveyed sheet and the cutting section in the sheet width direction prior to forming cut-outs of the fixed cut-out part in each sheet, whereby the cut-outs of the fixed cut-out part are formed in the same position in each sheet. forming, by the oblique cutout portion forming section, the oblique cutout portion (Va) by shifting the one of a conveyed sheet and the cutting section in a sheet width direction perpendicular to a sheet conveying direction by a shift amount (Δ) such that a position of a cutout on a second sheet is shifted by the distance relative to a position of a cutout on a first sheet, and to repeat this shifting step for each sheet until the oblique cutout portion has been formed; and forming, by the fixed cutout portion forming section, a fixed cut-out part (Vd) fixedly arranged in the vicinity of both edge parts of the sheet width direction by not shifting the one of a conveyed sheet and the cutting section in the sheet width direction prior to forming cut-outs of the fixed cut-out part in each sheet, whereby the cut-outs of the fixed cut-out part are formed in the same position in each sheet.