Surface plasmon resonance (SPR) biosensor has been used to detect many biochemical reactions, because this label-free sensor has high sensitivity and rapid response. The reactions are monitored by refractive index changes of the SPR biosensor. Iprovalicarb is protective, curative, and eradicative systemic fungicide introduced by Bayer AG in 1999. It has potential far control of downy mildew infesting onion, cucumber, grape and melon, late blight infesting tomato and potato, and anthracnose infesting watermelon and pepper. It is strictly limited to the maximum residue limit. In this study, the applicability of a portable SPR biosensor (Spreeta, Texas instrument, TX, USA) to detect the iprovalicarb residue was examined. The sensor chip was adopted to detect the reaction of iprovalicarb to immobilized iprovalicarb-antibody. The binding of the iprovalicarb onto the biosensor surface was measured by change of the refractive index (RI). Characteristics of the sensor chip including specificity, sensitivity, stability, and reusability were analyzed. In calibration test for seven levels of iprovalicarb concentration (0.32 to 5,000 mg/L) with three replications, a Sigmoidal model with Hill function was obtained between relative RI value and the iprovalicarb concentration with R-square of 0.998. It took 30 minutes to complete a set of detecting assay with the SPR biosensor.