An image forming apparatus has an envelope including as constituent elements first and second substrates spaced by some distance an electron source and an image forming member for forming an image upon irradiation of electrons from the electron source, the electron source and the image forming member being disposed in the envelope and a spacer for maintaining the distance between the first and second substrates, wherein the spacer is conductive and has a heat resistant organic polymer film formed on the surface of the spacer or the spacer is constituted of an insulating base member, a conductive film formed on the insulating base member, and a heat resistant organic polymer film formed on the conductive film.