To prevent deformation of a loop frame and upper/lower pressure receiving boards in pressing operating by reducing the stress to act on a loop frame and upper/lower pressure receiving boards in press by a press machine so as to execute pressing action in the state close to no stress.

The housing 1 of press machine is constituted of a loop frame 2 made of a looped material with steel plate stacked, a pair of upper/lower pressure receiving boards 3, 4 of roughly semicircle shape, a pair of side plates 5 and a tapered rib 6 for lock to surely hold the pressure receiving boards 3, 4. The loop frame 2 has looped shape and obtd. by coiling thin/long steel plate 50-100 turns. Further, the loop frame 2 is constructed with a pair of curved parts 2a respectively located vertically and a pair of straight parts 2b respectively located left/right, and pressing force of press machine is dispersedly received at the curved parts 2a. A plate thickness and plate width of loop material is arbitrarily decided corresponding to a size of the pressing force of press machine.