Abstract: The present invention relates to: reconstituted high-density lipoprotein nanoparticles comprising cholesterol; and a composition for preventing or treating Alzheimer's disease and cancer, the composition comprising the nanoparticles. Specifically, the reconstituted high-density lipoprotein nanoparticles comprising cholesterol according to the present invention have an excellent cell influx rate and promote cholesterol efflux from cells, thus having a cancer cell killing effect, and can therefore be used for preventing or treating cancer.