An upper die is removable in an up-down direction with respect to an upper die mounting groove that is arranged in a left-right direction at a lower part of an upper table of a press brake. The upper die includes a stop piece having a stop projection that is engageable with a stop groove that is formed in the left-right direction in each of upper die contact faces which face each other in a front-rear direction, the stop piece being movable out of and into a surface of the upper die and pushed in a direction to project out of the surface of the upper die. A bottom face of the stop projection for engaging with the stop groove is an inclined face that rises toward a front end of the stop projection.