A signal transmission circuit includes a transceiver, an impedance adjustment circuit, a first control circuit and a second control circuit. The impedance adjustment circuit realizes a low impedance state and a normal state of the transmission line. The first control circuit controls the impedance adjustment circuit to realize the low impedance state for a fixed period that is shorter than a width of one bit, when a change of a signal level on the transmission line is detected. The second control circuit controls the impedance adjustment circuit according to a transmission data transmitted from the transceiver, when detecting that a communication frame wins an arbitration by comparing the transmission data and the received data, to realize the low impedance state in an entire period where the signal level on the transmission line is recessive until transmission of the communication frame ends.