PURPOSE: To measure a pressure value in an optional place in a vacuum system by displaying a pressure value obtained by multiplying a coefficient to a pressure value shown by a signal obtained from a pressure measuring, sensor attached to an optional place in a vacuum system discharged by a discharging pump, as a pressure value of a place being different from a sensor attached place in the vacuum system.

CONSTITUTION: Places for measuring pressure in a vacuum system 10 are three points of A, B and C, and a sensor 12 is attached to the place A to which a sensor of a pressure measuring means can be attached easily, among them. An output of the sensor 12 is converted to a pressure signal in a measuring means 13, and used as a signal for displaying a pressure value PO of the point A on a display device 14a for constituting a pressure display means 14. Also, an output of the measuring means 13 is applied to operating circuits 15b, 15c, too, but the operating circuits 15b, 15c supply a display signal corresponding to a pressure value obtained by multiplying each prescribed coefficient K1, K2 to the pressure value PO shown by these applied signals, to indicators 14b, 14c of the pressure display means 14. As a result, pressure values P1, P2 corresponding to the point B and the point C are displayed on the display devices 14b, 14c, respectively.