The vacuum level of a chamber is measured by using the change of dark conductivity of amorphous silicon thin film with the pressure change of the chamber. The amorphous silicon pressure sensor for measuring the vacuum level comprises an amorphous silicon thin film (20) formed on glass substrate (10) by plasma enhanced chemical vapor deposition method; an amorphous silicon layer (30) formed on (20) by implanting the impurity of conductivity type; a metal electrode (40) formed on (30) by electron bean evaporation method. The thickness of the amorphous silicon thin film is 0.1-0.2 μm. The relation between the length of the metal electrode (L) and the separated distance of the metal electrodes (D) satisfy the following condition; L/D <= 20.
