An image forming apparatus comprises first and second substrates, a support frame arranged between the first and second substrates, and surrounding a space between the first and second substrates, electron emitting devices arranged on the first substrate facing the space, and an image forming member arranged on the second substrate. A spacer is disposed in the space between the first and second substrates, and a conductive film is arranged on the second substrate to surround the image forming member. The conductive film is supplied with a potential lower than that applied to the image forming member, and the spacer has a length greater than that of the image forming member. Each longitudinal end of the spacer is arranged between the inner periphery of the support frame and a respective plane through which a corresponding end of the conductive film extends perpendicularly to a principal surface of the second substrate.