Micelle is a soft aggregate of surfactants, and its boundary with the aqueous region is diffuse. All-atom molecular dynamics simulation is conducted in the present work to elucidate the effect of diffuseness of the micelle-water boundary on the distribution of hydrophobic solute bound to micelle. A restraining potential is applied to the headgroup atoms in surfactant for controlling the diffuseness of the boundary, and it is found that when the boundary is sharper, the micelle has less homogeneous structure and binds the hydrophobic solute through less flat free-energy profile with respect to the binding depth. (C) 2015 Elsevier B.V. All rights reserved.