PURPOSE: To eliminate the influence of magnetic field by measuring the degree of vacuum from the vapour coating speed of segment of material directly vapour coated and the vapour coating speed of segment of material indirectly vapour coated.

CONSTITUTION: Vapour coating material source 4 is vaporized by heating filament 5 and vapour coating speed measuring element 7a is directly vapour coated while vapour coating speed measuring element 7b shielded with shield 8 is vapour coated with a segment of vapour coating material 4 which collided with gas molecule in vacuum container 1. The ratio of the output of measuring element 7a against the output of measuring element 7b varies depending upon the density of gas molecule in vacuum container 1. As a result, resistance values of element 7a, 7b are differentiated through differentiation circuit 13 and the needle of meter 15 is made to swing with the differentiated ratio to measure the degree of vacuum.