A plasma process device for a generating a plasma in a container under reduced pressure and for processing an object. First and second electrodes are placed in opposed positions in the container. The electrodes are plate-like in shape. A protective member made of a stable material covers the first electrode. A means is provided for mounting the object to be processed on the second electrode. A first high-frequency power source is connected to the first electrode. A second high-frequency power source is connected to the second electrode. A gas supply for introducing desired gas into the container is provided. Frequency of the first high-frequency power source is higher than the frequency of the second high-frequency power source.