Disclosed is a nanopatch graphene composite, which includes graphene including a defect and a nanopatch positioned on the defect, and is configured such that a nanopatch is formed through a self-assembling process on the surface of graphene, thus improving the mechanical properties and durability of the graphene composite. Also, a flexible organic transistor, including the nanopatch graphene composite of the invention, is transparent and has high mechanical durability, thus exhibiting device stability, and the molecular alignment of the organic semiconductor layer growing on the nanopatch graphene composite is induced so as to become favorable for charge injection, thereby increasing the performance of the device.