PURPOSE: To increase the flatness of a bending product with the regulation of the deformation of the bend, waviness, etc. in plate thickness direction by providing the constraining guide at outlet side to regulate the deformation in the plate thickness direction due to the addition of the side bending force by a side roll on the outlet side of a rolling roll.

CONSTITUTION: The constraining guides 12, 13 at outlet side of the upper and lower parts are provided at the outlet side of the rolling rolls 7, 8 in the roll bending device to bend to the prescribed bending radius by delivering in pressing state with feeding between the rolling rolls 7, 8 by the inlet side guide table 2 a bending blank 1 and by pressing the side face by the side roll 21 which is arranged in the progressing direction thereof. The upper part outlet side constraining guide 12 moves vertically linking with the upper rolling roll 7 by being fitted to the upper metal chock 9 and the lower part outlet side constraining guide 13 is supported on the same level with the horizontal surface of the lower rolling roll 8 by roll frame 11 via the lower metal chock 10. The gap G' between said constraining guides 12, 13 is held is G'≥G against the gap G between the rolling rolls 7, 8.