To enable manufacturing a shelf provided with plural reinforced sections by forming specified grooves on a sheet metal panel through drawing working, executing continuous bending, and then forming an inverted isosceles triangle.

In a first deformation process, drawing forming is executed to form a C-shaped hollow body elongating along the whole length of the metal sheet 1. While the C-shaped hollow body is formed, the side parts 8 of the metallic sheet 1 repeatedly come nearer to each other to decrease a width of a reversed part 6. When an inverted isosceles triangle part 4 is formed as a result of continuous bending process, the side parts 8 come near to each other, and at the finish of the process both of the edged parts 9 of the recess 6 repeatedly approach each other. Thereby, a welding part 10 of adjacent two edged parts 9 is formed; thus single project 11 constituting a bending edge part of a shelf is formed.