Random nanopore and nanopillar patterns were prepared by using simple spin-coating technique based on the phase separation of a binary immiscible polymer blend of poly(amic acid) (PAA) and polyimide (PI). The pattern structure was spontaneously formed upon spin-coating of a mixed solution of PAA and PI on a glass substarte followed by thermal annealing, whose morphology was investigated by atomic force microscope and field emission scanning electron microscope technique. The results showed that not only the size of the patterns was the nanoscale of around 200 nm but also their shape was very uniform without requiring conventional patterning or photolithography processes. Two different morphologies, nanopore and nanopillar arrays were obtained for the PAA:PI volume ratio of 1:9 and 9:1, respectively. The flexible characteristic of nanopore and nanopillar films could be an interesting feature to be applied to organic light-emitting diodes lighting and displays.