PURPOSE: To measure the exhaust speed of an exhaust pump of a vacuum device and the conductance of an orifice with an easy operation in an inexpensive system, by measuring the exhaust time and the pressure of a rare gas in a vacuum vessel.

CONSTITUTION: A rare gas is packed in a porous base material 1 and the base material is coated to attain an exhaust speed measuring material 3, and this material 3 is provided in a vacuum vessel 5 connected to a vacuum exhaust pump 4 as an object to be measured, and the vacuum exhaust pump 4 is operated, and the pressure in the vacuum vessel 5 after the lapse of several hours is measured with a vacuum measurer 6. At this time, the change with time of a pressure P in the vacuum vessel 5 is given by an equation P=Cc.Pgo/S.exp (-Cc.t/Vg). In this equation, Cc, Vg, (t), and S are the conductance of a coating layer 2, the initial pressure of the rare gas packed in the porous base material 1, the exhaust time, and the exhaust speed, respectively. Consequently, only the exhaust time (t) and the rare gas pressure P are measured to measure easily the exhaust speed S and the conductance of the orifice.