According to one embodiment, a relay substrate provided between a liquid crystal panel and a controller includes first connectors. The controller includes a microcomputer and second connectors. The relay substrate and the controller include a line pattern to form a test circuit which feeds a test signal back to an input pin of the microcomputer from an output pin of the microcomputer, and which transfers the test signal between the controller and the relay substrate in each pair of the first connectors and the second connectors. The microcomputer outputs the test signal from the output pin, and determines a connecting state of the cables that connect the relay substrate and the controller based on a state of feedback of the test signal to the input pin.