Provided are a detector and a method of fabricating the same. The detector includes a base portion; first and second electrodes disposed on the base portion and spaced apart from each other; a reactant layer disposed between the first and second electrodes on the base portion to react with a specific functional group contained in a fluid; and a protection medium layer surrounding the first and second electrodes and forming a reaction space to expose a portion of the reactant layer. In the detector, electrodes can be effectively protected at low cost, and a path for guiding a fluid to be detected can be provided.