A gas sensor, a refrigerator having the gas sensor, and a method for controlling the gas sensor recognizes the ripening degree of a target food on the basis of a variation in color using a pH indicator having a color that is changed with pH variation generated when the pH indicator reacts with target gas, a refrigerator having the gas sensor. The gas sensor for detecting target gas includes: a base provided for gas permeation; and a detection unit provided at the base, and is discolored in response to pH variation generated when reacting with target gas having permeated the base.