This paper describes a flexible stamping method, which employs a flexible film stamp made of polymeric materials. Unlike conventional hard stamps, the flexible film stamp does not require either the stamp or its substrate to be perfectly flat, which means large area stamping is easy to achieve at reduced cost. We confirmed this by replicating 50 µm square multi-mode optical polymer waveguides. The propagation loss of the waveguide is only 0.06 dB/cm at a wavelength of 850 nm, which satisfies the basic requirement for optical circuit boards, and the waveguide was used to fabricate a flexible optical circuit board with mechanically transferable (MT) connectors.