PURPOSE: To provide a serial data transmission reception circuit in which the efficiency is excellent even when a transmission data quantity is less and the power consumption is reduced in the serial synchronization transmission sending serial data.

CONSTITUTION: A transmission section 10 is provided with a serial data transmission means generating and sending serial data and a clock generating means receiving a write signal to generate a transmission clock signal, and a reception section 20 is provided with a serial data reception means receiving the received serial data, and only when the transmission section 10 sends serial data, the transmission section 10 sends a transmission clock signal to the reception section 20, the transmission reception sections 10, 20 are operated, and when data are not sent to the reception section, the transmission reception sections 10, 20 are inactive.