To provide a technique capable of surely preventing filament disconnection.

When pressure is to be found on the basis of the magnitude of an ionic current I, by collecting ion formed by gas molecule ionization with a collector C after impressing positive voltage on the grid G of an ionization vacuum gauge 1 using an ionization vacuum gauge control device and producing thermion by heating a filament F, magnitude of a filament current If energizing through the filament F is directly detected by providing an overcurrent protection circuit 3 on the ionization vacuum gauge control device and the filament current If is limited so as not to exceed the specific upper value. It is possible to infallibly protect overcurrent because the filament current If can be limited without detecting an emission current Ie.