Nowadays, block copolymer is focused on because of its appicability to lithography. Some researchers developed photo-induced phase transition of block copolymer such as order-to-disorder, disorder-to-order. However, anyone couldn’t show photo-induced order-to-order phase transition. Here, I synthesized miktoarm block copolymer, (Polystyrene)2-b-Polymethylmetacrylate, containing photocleavable linkage. Before UV irradiation, the block copolymer is cylinder phase, even though the volume fraction of PS is 60%, because this miktoarm block copolymer can easily make curvature structurally. However, when the block copolymer is exposed to UV, the photocleavable linkage is cut, and then phase is changed to lamellea because it becomes similar to blending system. If I make the thin film by using this method, two kind of patterns can be fabricated on one substrate simultaneously.