Molecular logic gate device with "OR" logic function was developed. The "OR" function logic gate was fabricated by the double line structured bio-photodiode, depicted as A and B line, consisted of Green fluorescent protein/viologen/cytochrome c hetero-LB film. When a light was irradiated to a single (A or B) or double (A and B) line bio-photodiode as an input, the steady state photocurrent was generated in part of (A+B) as an output. The photocurrent intensity generated in one line input was lower than that of twin line input. The high photocurrent intensity indicates "1,1" in truth tables and low photocurrent indicates "0,1" or "1,0". Finally, "0,0" input corresponds to a dark state without light generation. The "OR" logic gate function was successfully achieved based on high- and low-photocurrent by threshold.