A plasma processing apparatus includes a view port to ensure ground continuity on a wall of a process chamber, so that uniformity of a process is enhanced. The view port of plasma processing apparatus includes a ground cover electrically connected to a wall of a chamber. The ground cover contacts the wall of the chamber to form contact surfaces, and the contact surfaces of the ground cover are constituted by bare surfaces. Accordingly, the ground continuity is ensured around the view port, thereby providing uniformity of an electric field and plasma within the chamber.