A binding machine comprising a clamp unit and a glue application unit arranged under a path of the clamp unit so as to apply glue to a back face (r) of a book block while the clamp unit passes through the glue application unit, the back face (r) protruding downwardly from the clamp unit, the glue application unit comprising: a frame; a glue tank attached to the frame and filled with glue; a glue application roller arranged in the glue tank and attached to the frame so as to rotate around a shaft thereof extending across the path of the clamp unit, the glue application roller applying the glue to the back face (r) of the book block; a motor attached to the frame and rotating the glue application roller, a part of the glue application roller being soaked in the glue of the glue tank, the glue application roller for engaging with the back face (r) of the book block at its top face covered with the glue; a wiper attached to the frame and arranged upstream of the top face of the glue application roller in a direction of rotation of the glue application roller in such a way that the wiper can contact and separate from an outer periphery of the glue application roller to adjust an amount of the glue covering the outer periphery of the glue application roller; a wiper drive mechanism attached to the frame so as to move the wiper; and a control unit for controlling the wiper drive mechanism, the wiper being movable between an open position in which the wiper is separated from the outer periphery of the glue application roller and a closed position in which the wiper is made to contact with the outer periphery of the glue application roller at a timing determined based on the information about a length of the back face (r) of the book block, the information about a position of the book block on the path of the clamp unit, a speed of movement of the book block, a distance from the top face of the glue application roller to the wiper in a circumferential direction of the glue application roller, and a speed of the outer periphery of the glue application roller, so that the back face (r) of the book block can engage with the top face of the glue application roller covered with the glue of the predetermined thickness while the book block passes through the glue application roller, wherein the control unit is suitable for controlling the wiper drive mechanism in operation such that the wiper is sequentially located at a first open position in which the wiper is separated from the outer periphery of the glue application roller by a first distance, a second open position in which the wiper is separated from the outer periphery of the glue application roller by a second distance which is shorter than the first distance, and the closed position during the passage of the book block through the glue application roller, whereby a leading end portion of the back face (r) of the book block engages with the top face of the glue application roller covered with the glue of a first thickness while middle and tail end portions of the back face (r) of the book block engages with the top face of the glue application roller covered with the glue of a second thickness which is smaller than the first thickness. a frame; a glue tank attached to the frame and filled with glue; a glue application roller arranged in the glue tank and attached to the frame so as to rotate around a shaft thereof extending across the path of the clamp unit, the glue application roller applying the glue to the back face (r) of the book block; a motor attached to the frame and rotating the glue application roller, a part of the glue application roller being soaked in the glue of the glue tank, the glue application roller for engaging with the back face (r) of the book block at its top face covered with the glue; a wiper attached to the frame and arranged upstream of the top face of the glue application roller in a direction of rotation of the glue application roller in such a way that the wiper can contact and separate from an outer periphery of the glue application roller to adjust an amount of the glue covering the outer periphery of the glue application roller; a wiper drive mechanism attached to the frame so as to move the wiper; and a control unit for controlling the wiper drive mechanism,