This invention provides a plasma tube array-type display device and a luminance correcting method realizing reduced variations in luminance values of a plasma tube array. A gradient of the luminance value in the longitudinal direction of one plasma tube is calculated on the basis of the obtained luminance value at a plurality of positions in the longitudinal direction of at least one plasma tube. A difference of the luminance value of each plasma tube obtained at the same relative position. On the basis of the gradient of the luminance value and the difference of the luminance value of each plasma tube at the same relative position, a correction luminance value in each discharge cell in the longitudinal direction of each of the plurality of plasma tubes is calculated.