An amphiphilic diblock copolymer with a narrow molecular weight distribution, which has a glucose residue-carrying vinyl ether subchain and an isobutyl vinyl ether subchain, was studied with its monolayer-forming properties at the air-water interface. The block copolymer and its blends with poly(isobutyl vinyl ether) homopolymer, spread from a mixture solution of chloroform and methanol onto the water surface, were found to form a stable monolayer. The surface monolayers were successfully transferred onto a substrate by the Langmuir-Blodgett technique, and the built-up film was characterized by surface plasmons and transmission electron microscopy. The surface pressure-area isotherms exhibited a plateau region, suggesting a structural change taking place on the water surface at specific pressures. The observed values of the layer thickness and the occupied area indicated that the hydrophobic segments, which lie essentially flat on the water surface at low surface pressures, aggregate at higher pressures, forming a thicker layer with hydrophobic and hydrophilic segments microphase-separated at the air-water interface. In addition, it was demonstrated that the layered structure of the LB film could be controlled by blending the homopolymer.