PURPOSE: To prevent the short circuit and deterioration in pressure resistance without largely changing the value of auxiliary capacitors by exposing the surfaces of auxiliary capacity electrodes and electrodepositing a high-polymer film in these exposed region.

CONSTITUTION: The surfaces of the auxiliary capacity electrodes 13 corresponding to the short circuit parts are exposed before display electrodes are formed and an insulating substrate 10 having these exposed auxiliary capacity electrodes 13 is inserted into an electrodeposition tank and while the auxiliary capacity electrodes are energized, the high-polymer film 34 is electrodeposited thereon. The resist by the electrodeposition sticks to the energized parts and, therefore, the resist is stuck to pinholes 33 in which the auxiliary capacity electrodes 13 are exposed when the substrate 10 is immersed into the electrodeposition tank and the auxiliary capacity electrodes 13 are energized. The pinholes 33 in which the auxiliary capacity electrodes 13 are not exposed but which are the cause for the deterioration of the pressure resistance are etched to expose the electrodes before the electrodeposition, by which resin is filled into almost all the pinholes 33.