To provide a novel work unfixing mechanism to reliably and smoothly implement the unfixing work to press a cast work from a mold.

When the work unfixing mechanism moves the cast work W while held by an upper mold 22a, presses it from the upper mold 22a by a pressing body 41, and unfixes the work, the pressing body 41 is set in a fixed condition to a support base 23 provided in an immobile condition during the stroke that the upper mold 22a unfixes the work W. On the other hand, the pressing body 41 is set to freely slide as the upper mold 22a is retracted during the stroke that the upper mold 22a is retracted to the height at which the work W placed on a carrying surface can be transferred after the unfixing, and when the pressing body 41 is switched in a free slide condition, the closely attached condition of a switching body 42 to the support base 23 generated by the pressing is eliminated mainly by the self-weight drop of the pressing body 41, and the switching is implemented.