The present invention relates to a secondary battery and an apparatus and method for measuring a dimension of the secondary battery. The secondary battery according to the present invention comprises: an electrode assembly in which an electrode and a separator are alternately laminated to be combined with each other; a pouch accommodating the electrode assembly therein; and a fluorescent reference marker applied to a portion of an outer surface of the pouch and comprising a fluorescent material, wherein the fluorescent reference marker emits fluorescence when an electromagnetic wave is irradiated so that the fluorescent reference marker serves as a reference point for measuring a dimension of the secondary battery.