PURPOSE: To cut off a slab part from a sheet material worked for microjoint by using a sheet bending machine.

CONSTITUTION: In the sheet bending machine which is provided with an upper and lower dies 8, 10 for holding a sheet material in between and with a bender 11 for bending a part of the sheet projecting from these dies 8, 10 by its vertical operation, a blade 17 for cutting the sheet material is provided in the bender 11. A sheet material W is brought into this sheet bending machine 1, on which material punching has been performed such that a slug part W' and a product part W" are connected with a joint (a) with a minute width; and this joint (a) is cut off with the cutting blade 17 of the bender 11 by the vertical operation of the bender 11. In the case where the joint (a) with a minute width is cut off by the sheet bending machine having a bender without a cutting blade 17, a clearance between the blade tip of the bender 11 and the upper/lower dies 8, 10 is set narrower than in the case of bending, and the bender is vertically operated similarly as in the case of bending.