A display panel driving device has a signal line driver. The signal line driver applies a pixel driving voltage based on an input image signal to each signal line of a display panel at a timing corresponding to a clock signal. The signal line driver is divided into a plurality of driver chips connected in cascade by the clock line. The display panel driving device supplies a clock signal through the driver chips. The duty ratio of the clock signal is stabilized when the clock signal passes through the driver chips, without leading to an increase in power consumption and in manufacturing costs.