To provide a manufacturing method of a metal case of connector that has resolved the problem of the current manufacturing method of the metal case.

The manufacturing method of a metal case of a connector includes (1) a cutting step of plate material, (2) a drawing press step for draw pressing the metal case frame opening having the bottom part closed on the plate material, (3) a bottom part punching step for cutting off the bottom part of the metal case frame opening that is draw pressed, (4) a side way trimming step in which the thin wall part at the bottom side edge part of the metal case frame opening is removed and the thickness of all sidewalls of the metal case frame opening is made uniform by trimming the burr, and the cross section of the sidewall is made shining smooth, (5) a folded-side forming step in which the bottom side edge part of the frame opening is folded down outside and made into a trumpet-shape with continuous folded-side, and (6) a later forming step, and a complete metal case having a shining smooth continuous folded-side frame opening is obtained.