To provide a cathode ray tube provided with an electron gun having an impregnated cathode structure with a high brightness and is capable of producing a precision electron flow density for a long time and having stable characteristics under any usage conditions.

The impregnant cathode structure is provided with a cathode pellet where a high melting-point metal porous substrate containing tungsten is impregnated with an electron emission substance whose main component is a double alkaline earth metal aluminate containing at least barium, and a high melting-point metal coat film provided on the electron emission surface of the cathode pellet. When the thickness of the high melting-point metal coat film is called Y (nm), and the operating temperature of the impregnated cathode structure is T (°C), and the operating temperature T is assumed 960°C or above, Y lies in the range surrounded by 960°C≤T and 4.666-×1010×10-1.100(T+273)≤Y≤1000, which is the hatched part in Figure 6.