A thread-rolling flat die for a threaded fastener, comprising a thread-rolling surface including at least a bite surface to which a workpiece of the threaded fastener is supplied, a finishing surface formed adjacent to the bite surface, and a roll-off surface formed adjacent to the finishing surface, the roll-off surface having an inclination with respect to the finishing surface, wherein the bite surface includes at least: a first partial bite surface having an inclination and an angle α of the inclination with respect to the finishing surface, the first partial bite surface being a portion for substantially forming a thread groove in a processed portion of the workpiece; and a second partial bite surface continuously formed between the first partial bite surface and the finishing surface, the second partial bite surface having an inclination and an angle β of the inclination with respect to the finishing surface, the angle β being smaller than the angle α; the thread-rolling flat die being characterized in that, in the first partial bite surface and the second partial bite surface, a crest angle of a processing tooth for forming a trough bottom of the thread groove in the threaded fastener is larger than a crest angle of a processing tooth in the finishing surface, wherein a crest shape of the processing tooth gradually changes from a root side to the crest angle of the processing tooth in the finishing surface along the thread-rolling surface from a starting point of the first partial bite surface toward the finishing surface, and wherein the length L1 of the first partial bite surface along a thread-rolling direction, the length L3 of the finishing surface along the thread-rolling direction, and the length L4 of the roll-off surface along the thread-rolling direction have a relationship of L1 > L3 > L4. wherein the bite surface includes at least: a first partial bite surface having an inclination and an angle α of the inclination with respect to the finishing surface, the first partial bite surface being a portion for substantially forming a thread groove in a processed portion of the workpiece; and a second partial bite surface continuously formed between the first partial bite surface and the finishing surface, the second partial bite surface having an inclination and an angle β of the inclination with respect to the finishing surface, the angle β being smaller than the angle α; the thread-rolling flat die being characterized in that, in the first partial bite surface and the second partial bite surface, a crest angle of a processing tooth for forming a trough bottom of the thread groove in the threaded fastener is larger than a crest angle of a processing tooth in the finishing surface, a first partial bite surface having an inclination and an angle α of the inclination with respect to the finishing surface, the first partial bite surface being a portion for substantially forming a thread groove in a processed portion of the workpiece; and a second partial bite surface continuously formed between the first partial bite surface and the finishing surface, the second partial bite surface having an inclination and an angle β of the inclination with respect to the finishing surface, the angle β being smaller than the angle α; the thread-rolling flat die being characterized in that, in the first partial bite surface and the second partial bite surface, a crest angle of a processing tooth for forming a trough bottom of the thread groove in the threaded fastener is larger than a crest angle of a processing tooth in the finishing surface, wherein a crest shape of the processing tooth gradually changes from a root side to the crest angle of the processing tooth in the finishing surface along the thread-rolling surface from a starting point of the first partial bite surface toward the finishing surface, and wherein the length L1 of the first partial bite surface along a thread-rolling direction, the length L3 of the finishing surface along the thread-rolling direction, and the length L4 of the roll-off surface along the thread-rolling direction have a relationship of L1 > L3 > L4.