Increase in power consumption and increase in power supply noise of a serial data input system are suppressed, while clock skew is more easily prevented. The serial data input system of this invention includes a shift register that takes in and shifts serially transferred display data in synchronization with a clock SCL, a clock counter that counts the number of clock pulses of the clock SCL and outputs each of clock count signals BIT08, BIT16 and BIT24 when the counted number of the clock pulses of the clock SCL reaches each of count numbers 8, 16 and 24 respectively, and registers into each of which the data stored in the shift register is transferred and stored collectively and in parallel in response to each of the clock count signals BIT08, BIP16 and BIT24 respectively.