A field effect transistor for detecting ionic material and a method of detecting ionic material using the field effect transistor. The field effect transistor for detecting ionic material includes a substrate formed of a semiconductor material, a source region and a drain region spaced apart from each other in the substrate and doped with an opposite conductivity type to that of the substrate, a channel region interposed between the source region and the drain region, an insulating layer disposed on the channel region and formed of an electrically insulating material, a first reference electrode disposed at an edge of the upper portion of the insulating layer and a second reference electrode disposed to be spaced apart from the insulating layer.