TESTING DEVICE, AND TESTING METHOD FOR THE LINE AND ONE SHEET USING THE TESTING DEVICE

A testing apparatus according to the present invention is a testing apparatus of a display device including a plurality of demultiplexing switches connected to each of a plurality of data lines, comprising: a one substrate testing device including a plurality of control switches connected to the demultiplexing switches through a plurality of lines; and a line testing device which supplies a line testing signal for detecting a failure in the lines to a pad which is connected to the control switches. The line testing device supplies a line testing signal to the pad to detect a failure in a plurality of first lines among the lines, and then detect a failure in the rest second lines among the lines. The first lines and the second lines are alternately arranged below the demultiplexing switches, such that a path for a signal transferred to the demultiplexing switches is formed.