The present invention aims to provide a monolithic driver-type display device capable of reducing circuit scale of a sampling circuit, and keeping low power consumption by directly driving a source driver with an externally provided video signal.In the monolithic driver-type display device having a display portion for displaying video and circuits for driving the display portion formed on the same insulating substrate, a plurality of sampling switches are provided in association with a plurality of pieces of bit data contained in externally inputted digital video signals. The sampling switches are opened/closed based on sampling signals, thereby sampling the digital video signals for each piece of the bit data and converting the signals into parallel format for output to data lines. The outputted digital video signals charge parasitic capacitances on the data lines and are held therein.