NOVELTY - The method comprises forming a flexible printed circuit board, forming a first electrode on the flexible printed circuit board as a reflection anode, forming a hole extract layer from a sol-gel p-type material in the first electrode, forming a nano pattern in the hole extract layer, forming a photoactive layer in an upper side of the hole extract layer, forming an electron extract layer in an upper side of the photoactive layer, and forming a second electrode as a cathode present in an upper side of the electron extract layer. The nano pattern is formed using nano-imprint mold.    USE - The method is useful for manufacturing a flexible organic solar cell (claimed).    ADVANTAGE - The method is capable of economically manufacturing the flexible organic solar cell with high productivity and efficiency.    DETAILED DESCRIPTION - The method comprises forming a flexible printed circuit board, forming a first electrode on the flexible printed circuit board as a reflection anode, forming a hole extract layer from a sol-gel p-type material in the first electrode, forming a nano pattern in the hole extract layer, forming a photoactive layer in an upper side of the hole extract layer, forming an electron extract layer in an upper side of the photoactive layer, and forming a second electrode as a cathode present in an upper side of the electron extract layer. The nano pattern is formed using nano-imprint mold. The hole extract layer has a thickness of 1-100 nm. The nano pattern has anodized aluminum oxide or anisotropic crystalline structure. The metallic foil is formed as a separation section in the flexible printed circuit board, and connected with a motherboard. The nanopattern is formed: using anodic aluminum oxide, sulfuric acid, oxalic acid and phosphoric acid; and changing a concentration of components by applying a voltage of 20-200 V to form nano-holes. The deposition is carried out by vacuum deposition method, electronic beam evaporation, thermal evaporation, sputtering method, laser deposition method, organic chemistry deposition method or chemical vapor deposition technique. The nano pattern has a nanostructure having diameter of 10-500 nm. The motherboard is made of glass, metal, or polymer material.