Disclosed herein is a device for cutting a glass sheet, continuously supplied after a melting and solidification process, into quadrangular glass substrates. The glass sheet cutting device includes two or more cutters for cutting a glass sheet into quadrangular glass substrates, a defect inspector for scanning the glass sheet to three-dimensionally check defect positions in a length direction, a width direction and a thickness direction of the glass sheet, a position adjuster for moving at least one of the cutters to a portion of the glass sheet at which few defects are distributed, and a controller for informing the position adjuster of positions of the cutters based on the scanned results received from the defect inspector.