A buttonholing machine comprising: a knife provided on a bed portion and formed with a cutting edge on an upper end thereof; a feed table provided on the bed portion and having an upper surface on which a workpiece is placed; a hammer provided on an arm portion to face the knife, wherein the knife and the hammer sandwiches the workpiece therebetween to cut the workpiece; an actuating mechanism which moves the hammer toward or away from the knife; a driving device coupled to the actuating mechanism, wherein the driving device drives the actuating mechanism when a current is applied thereto; and control means for controlling a driving operation of the driving device, wherein, before or after forming, on the workpiece, buttonhole stitches including right and left side stitching sections, the control means controls the driving device to move the hammer toward the knife to form a buttonhole through the workpiece between the right and left side stitching sections, characterized by further comprising: stress detecting means for detecting a stress (σn) applied to the knife when forming the buttonhole; cumulating means for cumulating, each time the buttonhole is formed, the stress (σn) detected by the stress detecting means to calculate a cumulated stress (Σσn); storing means for storing a threshold stress (σa) that causes a wear-out or a breakage of the knife; and informing means for informing a user of a replacement of the knife, wherein, when the cumulated stress (Σσn) reaches the threshold stress (σa) or before the cumulated stress (Σσn) reaches the threshold stress (σa), the control means controls the informing means to inform the user of the replacement of the knife. a knife provided on a bed portion and formed with a cutting edge on an upper end thereof; a feed table provided on the bed portion and having an upper surface on which a workpiece is placed; a hammer provided on an arm portion to face the knife, wherein the knife and the hammer sandwiches the workpiece therebetween to cut the workpiece; an actuating mechanism which moves the hammer toward or away from the knife; a driving device coupled to the actuating mechanism, wherein the driving device drives the actuating mechanism when a current is applied thereto; and control means for controlling a driving operation of the driving device, wherein, before or after forming, on the workpiece, buttonhole stitches including right and left side stitching sections, the control means controls the driving device to move the hammer toward the knife to form a buttonhole through the workpiece between the right and left side stitching sections, characterized by further comprising: stress detecting means for detecting a stress (σn) applied to the knife when forming the buttonhole; cumulating means for cumulating, each time the buttonhole is formed, the stress (σn) detected by the stress detecting means to calculate a cumulated stress (Σσn); storing means for storing a threshold stress (σa) that causes a wear-out or a breakage of the knife; and informing means for informing a user of a replacement of the knife, wherein, when the cumulated stress (Σσn) reaches the threshold stress (σa) or before the cumulated stress (Σσn) reaches the threshold stress (σa), the control means controls the informing means to inform the user of the replacement of the knife. stress detecting means for detecting a stress (σn) applied to the knife when forming the buttonhole; cumulating means for cumulating, each time the buttonhole is formed, the stress (σn) detected by the stress detecting means to calculate a cumulated stress (Σσn); storing means for storing a threshold stress (σa) that causes a wear-out or a breakage of the knife; and informing means for informing a user of a replacement of the knife, wherein, when the cumulated stress (Σσn) reaches the threshold stress (σa) or before the cumulated stress (Σσn) reaches the threshold stress (σa), the control means controls the informing means to inform the user of the replacement of the knife.