An electronic light radiation tube wherein a cathode and an anode disposed as spaced from each other by a small spacing are housed in an envelope enclosing therein a luminous gas, and a magnetic field is applied to the envelope so as to cause magnetic lines of force of the magnetic field to pass through the envelope, while the magnetic lines of force which have passed through the cathode are prevented from passing through the anode, whereby electrons emitted from the cathode are caused to collide at a high efficiency with the luminous gas throughout the entire interior space of the envelope to excite the gas, and highly uniform light radiation can be realized over the entire envelope.