Provided are a FET-based sensor for detecting an ionic material, an ionic material detecting device including the FET-based sensor, and a method of detecting an ionic material using the FET-based sensor. The FET-based sensor includes: a sensing chamber including a reference electrode and a plurality of sensing FETs; and a reference chamber including a reference electrode and a plurality of reference FETs. The method includes: flowing a first solution into and out of the sensing chamber and the reference chamber of the FET-based sensor; flowing a second solution expected to contain an ionic material into and out of the sensing chamber while continuously flowing the first solution into and out of the reference chamber; measuring a current in a channel region between the source and drain of each of the sensing and reference FETs; and correcting the current of the sensing FETs.