PURPOSE: To provide the method for bending a sheet material constituted of metals or ceramics, etc., with high accuracy.

CONSTITUTION: A metallic film 6 is formed by utilizing thermal spraying, sputtering, etc., of metals on the surface of the bent part of the sheet material 1. Further, a large temp. gradient is generated in the irradiated part when the metallic plate 6 is irradiated with a laser beam 4. The sheet material to be worked is bent to the side of the part irradiated with the laser in its bent part at the time of cooling in the post stage. The plastic deformation quantity thereof can be controlled with high accuracy by setting optimum laser conditions. On the other hand, the abrupt internal stresses generated at this time are applied on the metallic part of the sheet material to be worked and, therefore, the cracking of the sheet material to be worked and the breakdown of the sheet material itself do not arise.