The present invention relates to an anticancer drug-encapsulated micelle agent composition, the composition comprising, relative to 100 parts by weight of anticancer drug-encapsulated polyethylene glycol-polylactide-polyethylene glycol polymer micelles, 0.3-0.7 parts by weight of polyethylene glycol having a weight average molecular weight of 1,500-2,500 and 0.3-0.7 parts by weight of mannitol. The micelle agent composition can be provided by successful reconstitution of anticancer drug-encapsulated PEG-PLA-PEG micelles after lyophilization thereof, thereby suggesting a substantial anticancer nanodrug for storage, minimizing systemic toxicity, and providing sustained drug release, leading to a maximization of anti-tumor effects.