There is provided a portable measuring system having a biophotonic sensor. The portable measuring system also includes a tunable light source, an output intensity detector and an output wavelength detector, which are mounted therein. The portable measuring system can precisely measure a variation in the reflectivity spectrum and/or the transmittance spectrum of the biophotonic sensor before and after an antigen-antibody reaction by varying the wavelength of the tunable light source. Thus, the concentration of the antigen is precisely measured.