For aging a cathode-ray tube which has a cathode capable of emitting an electron beam, a first electrode for limiting the electron beam, a second electrode for accelerating electrons of the limited electron beam, a third electrode for focusing the accelerated electron beam and an anode, the cathode is energized so that an electron beam is emitted therefrom while D.C. rated voltages are applied to the first and second electrodes, respectively, and first and second voltages are applied to the third electrode and the anode, respectively, for a predetermined time. The first and second voltages are time-varying within first and second zones each of which is between a first level lower than the D.C. rated voltage on the second electrode and a second level higher than the highest one of the voltages on the third electrode with which an electric current flows in the second electrode with the electron beam emitted from the cathode. The first time-varying voltage is in phase with and lower than the second time-varying voltage. The first time-varying voltage is varying so as to be at a level between the first and second levels at least for a part of the above-mentioned predetermined time.