We have prepared poly(4-terl-butylstyrene-block-4-tert-butoxystyrene), BO, having very bulky and hydrophobic substituent in both components by an anionic living polymerization. The BO films with various thicknesses were prepared by the spin-coating method from toluene solutions, and they were annealed under vacuum above the glass transition temperatures of both two components. An alternating lamellar structure oriented normal to the surface was observed at the surface of the BO film with thickness more than 150 nm, where the appearance of both B and O components were confirmed by XPS measurements. it is revealed that the ordered surface structure is caused by nanophase separation of BO clearly proved by hydrolyzed surface structures. Another aspect of this work is the structure of BO block copolymer after hydrolysis reaction. The O component can be easily converted into poly(4-hydroxystyrene) which has an ability to form a hydrogen bond. Moreover, it turns out that the control of the hydrolyzed layer thickness is possible by choosing the solvents in the reaction. This hydrophilic-hydrophobic nanopatterning is expected to be useful in a template of assembling nanoparticles and peptides.