A buttonhole machine (1) comprising: a knife (50) which cuts a workpiece; anda knife receiver (30) disposed opposite the knife (50), the knife (50) and the knife receiver (30) pressing the workpiece therebetween to cut the workpiece with the knife (50), before or after Forming buttonhole stitches on the workpiece, one of the components, which are the knife (50) and the knife receiver (30), is moved towards the other one to form a buttonhole through the workpiece, characterized by further comprising: a cloth cutting drive means (11) coupled to the knife (50) or knife receiver (30) for reciprocating the knife (50) or the knife receiver (30); a control means (7) which drives the Cloth cutting drive means (11) controls when the buttonhole is formed; a movement amount detecting means (12) which detects an amount of movement of the knife (50) or the knife receiver (30); a load detecting means (60) which detects a movement amount Load applied between the blade (50) and the blade receiver (30) over the workpiece; a load increase rate storing means (72) which detects a threshold of a rate of increase of the load with respect to the amount of movement of the blade (50) or blade receiver (30) stores; anda determination means (7) which determines whether the rate of increase of the load with respect to the amount of movement of the blade (50) or the blade receiver (30) during a buttonhole forming operation has reached the threshold stored in the load increase rate storing means (72) the determining means (7) determines that the rate of increase of the load with respect to the amount of movement of the blade (50) or blade receiver (30) has reached the threshold, the control means (7) reversely drives the cloth cutting drive means (11) to move the blade (10). 50) and the blade receiver (30) to separate.
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