A mask of a display device for forming a light shielding unit, which includes a first column spacer, a second column spacer, a light shielding layer, and a first groove, is capable of reducing the number of tones therein, the mask including: a first portion corresponding to the first column spacer; a second portion having substantially a same light transmittance as that of the first portion and corresponding to the second column spacer; a third portion corresponding to the light shielding layer; a fourth portion corresponding to a pixel region; and a fifth portion disposed between the first portion and the third portion to correspond to the first groove and having a light transmittance substantially the same as that of the fourth portion.