An oxide cathode for an electron tube and a method for manufacturing the oxide cathode are provided. In the oxide cathode including a sleeve for a heater, a metal substrate formed on the top of the sleeve, and an electron emission material layer coated on the metal substrate, the electron emission material layer is formed by coating a carbonate paste containing an alkaline earth metal carbonate, an organic blowing agent, and a vehicle on the metal substrate by screen printing, and thermally treating the coated carbonate paste. Picture quality degradation due to a Moire phenomenon is reduced by coating the carbonate paste by screen printing to provide an even cathode surface, and degradation of the cathode by Joule heat is reduced, thereby improving electron emission and lifespan characteristics of the cathode.