To reduce maintenance costs, by setting a boss part having one end fixed to a connection part of a pressure introduction tube to a diaphragm seal unit, a needle part connecting the diaphragm seal unit, and the pressure introduction tube, etc.

A boss part 24 has one end secured to a connection part where capillary tubes 6, 9 (pressure introduction tubes) are connected to diaphragm seal units 7, 11. A cap unit part 27 is engaged with the boss part 24, thereby fixing the boss part 24 to a pressure introduction pipe 21. In order to unite the diaphragm seal units 7, 11 with the capillary tubes 6, 9, the cap nut part 27 is screwed to a screw part of the pressure introduction pipe 21. As a result, a needle part 28 penetrates a rubber material 22, connecting interiors of the diaphragm seal units 7, 11 and the capillary tubes 6, 9 and allowing sealed liquids 8, 12 to move. The diaphragm seal units 7, 11 and capillary tubes 6, 9 can be exchanged as a unit for inexpensive maintenance.