PURPOSE: To improve the dimensional accuracy of a drawn plate by cutting the end parts of flanges extending vertically as far as joining parts simultaneously as well as the end parts of the joining parts when the end parts of the drawn plate is cut.

CONSTITUTION: At a 1st stage, a steel plate member is worked to form flanges 2 extending in the lengthwise direction and the drawn plate 15 having stepped joining parts 13, 14 formed at both ends of the flanges. At a 2nd stage, the ends of the joining parts 13, 14 are cut in a prescribed shape. At a 3rd stage, the cut drawn plate 15 is bent in an annular shape and the joining parts 13, 14 are welded to make the whole body in a cylindrical shape. Then, when the drawn plate 15 by the 2nd stage is cut, the end parts of the flanges 2 extending vertically as far as the joining parts 13, 14 as well as the end parts of the joining parts 13, 14 are cut simultaneously. Thus, no stepped parts can be formed in the welded part.