To provide adjustable positioning blocks in press dies, by which adjustable positioning blocks, the accurate positioning can be easily performed using the same positioning blocks even when the shape and size of a workpiece are different.

The plate-shaped workpiece 10 is fixed on the die 1 by bringing the four peripheral edges of the plate-shaped workpiece 10 into contact with the side surfaces of the positioning blocks 9 uprightly stood around the four peripheral edges of the workpiece so as to be dismountable. The positioning blocks 9 are composed of an inserting column body 5 having a cross section of a regular polygon and a pin portion 8 having positioning peripheral surfaces 7 formed so as to have the same number of surfaces as those of the inserting column body 5, wherein the peripheral surfaces of the inserting column body 5 are parallel with the positioning peripheral surfaces 7 via stepped portions, and the distances d of the parallel steps for the respective surfaces are different respectively.