A bookbinding apparatus for trimming sheets includes an adhesive applying device for applying adhesive to a back of the sheets; a trimming blade disposed in a trimming position; a bunch position changing device disposed in a transport path to change a position of the sheets in the trimming position; a blade receiving member having at least first and second blade receiving areas with different blade receiving surfaces contacting with the trimming blade; a driving device positioning the trimming blade between a cut position for bringing the trimming blade into contact with the blade receiving member and a spaced waiting position; a shift device selectively shifting one of the first and second blade receiving areas to a predetermined trimming position, and a control device for controlling the shift means and the driving means.