A communications apparatus serially transmitting a code string including a target code includes a converter to convert first codes in the code string into second codes having bit strings longer than those of the first codes, and having first polarities and second polarities with a bit string reversed from that of the first polarity, and a transmitter to serially transmit bits of the converted second codes in order from lower-order bits. When the second code includes a number of “0” bits equal to that of “1” bits, the converter converts the second code into a second code having a polarity identical to that of a previously transmitted second code. When the second code includes the number of “0” bits differing from that of “1” bits, the converter converts the second code into a second code having a polarity differing from that of the previously transmitted second code.