A flat-type fluorescent lamp includes a lamp body and a first external electrode. The first external electrode is positioned on an end portion of the lamp body. The first external electrode includes a main electrode portion and a first auxiliary electrode portion. The main electrode portion crosses end portions of the discharge spaces. The first auxiliary electrode portion protrudes from the main electrode portion. The first auxiliary electrode portion corresponds to an outer discharge space adjacent to a side of the lamp body. Therefore, a luminance of the flat-type fluorescent lamp may be made more uniform, thereby improving an image display quality. In addition, operation of the flat-type fluorescent lamp at a low temperature may be improved.