To prevent a malfunction of a pressure sensor by fitting a strain gauge to the pressure sensor fitted to a ram cylinder, and providing a surge pressure absorption part on a pressure inlet formed opposite to the strain gauge to absorb the instantaneous surge pressure generated in the pressing action.

A strain gauge 18 is fitted to a pressure sensor 7 fitted to a ram cylinder 2, and a surge pressure absorption part SAB is provided on a pressure inlet 15 formed opposite thereto. An orifice joint 16 is screwed in an outer side of a body 14 of the pressure sensor 7, and a relatively long drawing part 21 and a wide oil pan 17 to be communicated therewith are formed therein to constitute the surge pressure absorption part SAB. The pulsation wave M of an oil with a large surge pressure S is absorbed while the oil passes through the long drawing part 21, and diffused in the wide oil pan 17 to increase its volume, and the surge pressure S is absorbed thereby. The oil whose surge pressure is absorbed reaches the pressure inlet 15, and only the actual pressure E is applied to the pressure inlet 15.