A method of electrically inspecting semiconductor display devices, which is capable of inspecting whether a signal is normally input to the pixels and whether an electric charge is normally held by the holding capacitors without using the video signal line as a passage for reading the electric charge and without separately providing an inspection-dedicated circuit.Power source lines which are used as passages for supplying the power source voltage are used as passages for reading the electric charge. Namely, the power source lines that can be connected to the signal lines are used as passages for inputting an inspection signal to the holding capacitors in the pixels and for reading the electric charge from the holding capacitors in the pixels.