PURPOSE: To generate a stabilized preliminary discharge at all times by closely attaching a couple of preliminary discharge electrodes of a discharge trigger respectively to a common insulating material, and generating the preliminary discharge as a creeping discharge along the surface of the insulating material.

CONSTITUTION: Two preliminary discharge electrodes 12 of a discharge trigger 5 are closely attached to the surface of a common insulating material 11 with a specified gap 13 in between to form a trigger electrode 14. One electrode 12 is connected to a high-voltage electrode 7, and the other electrode 12 to a counter electrode 8. The discharge trigger 5 of this constitution is set in a sputtering device, a voltage is impressed between a target 2 and a substrate 3 from a plasma power source 4, and a high voltage is impressed on the discharge trigger 5 from a trigger power source 6. As a result, a creeping discharge is generated along the surface of the material 11, plasma is produced between the target 2 and the substrate 3 with the creeping discharge as an ignition source, and sputtering is started. Since a stabilized preliminary discharge can be generated by the discharge trigger 5, the operation of the sputtering device is highly stabilized.