A slight pivoting movement makes a rotary cam out of a predetermined forming position, making an unwanted step in a curved surface of the work or making unable to form into an accurate curve. Sometimes, providing a product of accuracy in the order of {fraction (1/100)} mm was difficult, or it was impossible to provide a formed sheet metal product of a high quality. The present invention aims to maintain the rotary cam at a predetermined forming position thereby providing a formed sheet metal product of a high quality. The present invention provides a negative-angle forming die comprising a lower die half having a supporting portion for placing a sheet metal work, and an upper die half to be lowered straightly downward onto the lower die half for forming the work, an intrusion forming portion formed in the lower die half at an edge portion near the supporting portion inward of a downward stroke line of the upper die half, a rotary cam rotatably provided in the lower die half, a slide cam including an intrusion forming portion and slidably opposed to the rotary cam, and an automatic retractor provided in the lower die half for pivoting the rotary cam back to a position thereby allowing the work to be taken out of the lower die half after a forming operation, the work placed on the supporting portion of the lower die half being formed by the intrusion forming portion of the rotary cam and the intrusion forming portion of the slide cam, the slide cam forming the work by sliding, the automatic retractor pivoting back the rotary cam after the forming operation for allowing the work to be taken out of the lower die half, wherein the rotary cam has two ends each including a supporting shaft projecting therefrom, the supporting shafts being supported by the lower die half for rotatably supporting the rotary cam, positioning means for fixing an axial position of the rotary cam being provided in the lower die half and the rotary cam.