Disclosed herein is an optical circuit-type reformulated fuel detecting sensor device. The optical circuit-type reformulated fuel detecting sensor device includes: an optical source part generating optical signals having a single wavelength; a sensor part receiving the optical signals generated by the optical source part and outputting a reference optical signal and a sensed signal; a first photo-detector receiving the reference optical signal and outputting a reference optical output signal; a second photo-detector receiving the sensed signal and outputting a sensed optical output signal; an operation controlling part receiving the reference optical output signal and the sensed optical output signal and determining characteristics of fuel; and an output part receiving and outputting a result of the operation controlling part.