Polymeric micelles are invaluable media as drug nanocarriers. Although knowledge of an interaction between the micelles is a key to understanding the mechanisms and developing the superior functions, interaction potential surface between drug-incorporated polymeric micelleshas not yet been quantitatively evaluated due to the extremely complex structure. Here, interaction potential surface between drug-entrapped polymeric micelles was unveiled by combining a small-angle scattering experiment and a model-potential-free liquid-state theory.Triblock copolymer composed of poly(ethylene oxide) and poly(propylene oxide) was investigated over wide concentration range (0.5-10.0wt%). Effects of entrapment of waterinsoluble hydrophobic drug, cyclosporin A, on the interaction were explored by comparing the interactions with and without the drug. The results directly clarified the high drug carrier efficiency in terms of the interaction between the micelles. In addition, investigation based on density functional theory provided a deeper insight into the monomer contribution to the extremely stable dispersion of the nanocarrier.