An antioxidant sensor includes a pressure sensor configured to obtain a contact pressure between an object and an optical sensor; the optical sensor configured to, based on the obtained contact pressure exceeding a set threshold pressure, emit a first light of a first wavelength to the object, and receive the first light reflected or scattered from the object; and a processor configured to determine a contact portion of the object in contact with the optical sensor, set a threshold pressure, among different threshold pressures, according to the determined contact portion, and determine an antioxidant value based on the received first light.