To perform not only a continuous vacuum inspection but also a total inspection of products by applying a high voltage into a sealed and evacuated non-conductive vessel from the outside to cause a plasma state within the vessel, and detecting the change of electric field or plasma emission before and after plasma generation.

When electrodes 24, 30 are arranged on the outer surface of the body side part of a vessel 10, and a high voltage is applied thereto, a plasma state occurs in the hollow part of the vessel 10, and a low atmospheric pressure condition is given thereto, whereby a vacuum discharge phenomenon can be easily provided. Paying attention to the electric field generated by the high voltage application, the electric change based on the change of field intensity is taken as electric signal to detect the vacuum of a subject vessel. A plasma detection part 14 has a detection part 36 for outputting the change of the electric field as a signal, and the detection signal is compared with a set value set from the relation between atmospheric pressure and voltage to judge the quality of vacuum in conformation to the generation of plasma. Thus, a continuous product total inspection can be performed in a short time.