Abstract: In a flat cathode ray tube, a flat glass tube is of three-element structure includes a screen panel integrally provided with skirt portions which are erected from the screen panel along the front end and the opposite side portions thereof continuously, a front panel or a back panel of a sheet-like configuration, and a funnel portion having a neck portion. The screen panel, front panel and funnel portion are combined through frit glasses, and a phosphor screen is formed on the inner surface of the screen panel. An electron gun is disposed within the neck portion, so that an electron beam generated from the electron gun collides with molecules within the flat glass tube to generate negative ions. The negative ions are accelerated and irradiated at the center portion on the skirt portion provided at the front end of the screen panel, whereby the phosphor screen is prevented from being burned by the ions and degradation of the frit glass due to impact of the negative ions is prevented.