Display device and method of inspecting display device

A display device comprising:

• a panel unit comprising a display unit comprising pixels for displaying an image, a first circuit board connected to the display unit, and a first connecting member connected to the first circuit board;
• an input unit comprising a connection member configured to be attached to the first connecting member, and to provide an image signal to the panel unit;
• a master configured to output a transmitting signal for diagnosing an electrical connection between the first connecting member and the connection member;
• a transmitting line connected to the master;
• an inspecting line configured to be connected to the transmitting line through the connection member;
• and
• a slave configured to be connected to the master through the inspecting line, to receive the transmitting signal as a receiving signal, and to enable determination of an on-time duty and an off-time duty of the receiving signal to determine whether a connection error between the panel unit and the input unit exists.