To reduce breaking and wear of a chamfer of a tooth of a form rolling die by reducing a load on the chamfer of the tooth to lengthen a life thereof.

A tooth part 22 of a leading tooth group of a form rolling flat die 21 is configured to perform form rolling work on an outer circumferential surface of a workpiece and is provided with a chamfer 24 at one end in the tooth width direction of a tooth tip part 11. A width W of the chamfer is increased gradually in accordance with an increase in tooth height h. A locus 26 of a connection part 25 of the tooth tip end and the chamfer is approximated by a straight line or curved line. A chamfer angle formed by a horizontal plane viewed in the form rolling direction of the chamfer and the chamfer is kept at a fixed angle for approximation by a straight line. Alternatively, a rate of increase in the width direction is increased gradually in accordance with an increase in tooth height for approximation by a curved line. Alternatively, the chamfer angle is reduced gradually.