To provide a flat die for roll-forming with which even in the case of finely tilting the positional relation of one pair of the flat dies, a strain caused by the elastic-returning of the flat dies for roll-forming is prevented without sacrificing the service life of the flat die and the error of accumulated pitch is decreased and the high precise formed precision can be obtained.

An addendum line 9 of a chamfer inclined tooth part 4, is inclined to a shifting direction F of the flat die and the tooth at the front-half part 2 of the chamfer inclined tooth part 4 is made to entrench only in the tooth height direction, and a pitch line 11 and a tooth bottom line 17 at the front-half part 2 of the chamfer inclined tooth part 4 are largely inclined respectively to the reverse direction of the addendum line 9 of the chamfer inclined tooth part 4. The addendum line 9 of the tooth at the rear-half part 3 of the chamfer inclined tooth part 4 is on the addendum line 9 of the chamfer inclined tooth part 4, and the pitch line 10 and the tooth bottom line 18 of the tooth at the rear-half part 3 of the chamfer inclined tooth part 4 is made to entrench in the tooth height and the tooth surface directions by parallel inclining in the same direction to the addendum line 9 of the chamfer inclined tooth part 4.