[1] We have found that efficient acceleration of resonant electrons takes place in a self-consistent particle simulation reproducing whistler-mode chorus emissions. While the majority of electrons lose energy contributing to the generation of chorus emissions, a fraction of resonant electrons having large pitch angle are simultaneously energized through nonlinear wave trapping by the generated chorus emissions. A small fraction of energetic electrons are energized over 100 keV during 2500 Omega(-1)(e0). We also find that such accelerated electrons show a characteristic behavior turning their motion from equatorward to poleward during the acceleration process, which is explained by the relativistic turning acceleration (RTA) process. The present study clarifies that the role of nonlinear wave trapping is significant in the energization process of relativistic electrons by narrowband whistler-mode chorus emissions.