A serial communication interface device includes a converter, a transmitter, and a receiver. The converter generates a first signal and a second signal based on changes in a clock signal, and a third signal and a fourth signal based on changes in a data signal, converts into the clock signal and the data signal based on the first to the fourth signals, sets the transmission start signal in response to receiving the fourth signal during a period where the clock signal is a first level, and sets the transmission end signal in response to reception of the third signal after reception of the first signal. The transmitter converts the first to the fourth signals into a communication signal and transmits the communication signal to a communication line. The receiver converts the communication signal received from the communication line into the first to the fourth signals.