A micro resonator sensor includes a main waveguide, a resonance waveguide and optical path changing means. Optical path changing means are installed at apex regions contacting with adjacent optical waveguides forming the resonance waveguide and reflect at least a part of the split optical signal inputted into the resonance waveguide to circulate the split optical signal inside the resonance waveguide. The micro resonator sensor can be manufactured without an excessive radiation loss and can be manufactured as an on-chip.