The present invention relates to: a plant with improved nitrogen use efficiency through the induction of double activation tagging mutants of ammonium transporter and glutamate synthetase genes; and a method for producing the plant. Compared to wild-type or other transformed plants, the plant according to the present invention shows, in all phases of plant growth, a significant increase in nitrogen use efficiency in terms of nitrogen uptake, assimilation, and remobilization, for example, thus significantly increasing growth rate, biomass, and grain yield. The transformed plant can increase crop yield under nitrogen-limited conditions, while also reducing the amount of fertilizer used, and can improve the quality of the crop. Therefore, the transformed plant can be useful in the fields of agriculture and foodstuffs.
