We report a near-field microwave biosensor based on a dielectric resonator to detect glucose concentration. A microwave biosensor with a high Q dielectric resonator allows observation of the small variation of the glucose concentration by measuring the shift of the resonance frequency and the microwave reflection coefficient S(11). We observed the concentration of glucose with a detectable resolution up to 5 mgml at an operating frequency of about f=1.68 GHz. The change in the glucose concentration is directly related to the change in the reflection coefficient due to the electromagnetic interaction between the dielectric resonator and the glucose solution.