A signal transmission apparatus may transmit and receive a differential signal using transmission lines. The apparatus may include a transmitter and a receiver. The transmitter may transmit a mixed signal obtained by mixing the differential signal with a single ended signal. The receiver may restore the differential signal and the single ended signal from the mixed signal. An edge of the single ended signal may have a phase difference of about 90° with an edge of the differential signal. The signal transmission apparatus and method may transmit two signals through a single channel to reduce a circuit area.