A mask repairing apparatus may include a stage, a stereoscopic imaging unit to measure a stereoscopic image of a mask on the stage, a control unit to compare the stereoscopic image with a normal image of the mask and to produce a defect image of the mask, and a laser unit to irradiate a laser beam onto a deficient part of the mask, under control of the control unit. The control unit may control the laser unit, based on the defect image, such that the laser beam is sequentially irradiated onto m multiple layers of the deficient part while repeatedly moving in a first direction and a second direction crossing each other.