To transmit mixed signals of different bit rates, at a low cost.

A header attaching unit 102 attaches to data of a low-speed bit rate A, a header of the bit rate A. A header attaching unit 103 attaches the header of the bit rate A to data of a high-speed bit rate B. A combining unit 104 combines outputs of the header attaching unit 102 and the header attaching unit 103. A low-speed scrambler 105 performs scrambling process on combined data, by using a clock corresponding to the bit rate A. A high-speed scrambler 106 performs a scrambling process on the data of the bit rate B, by using a clock corresponding to the bit rate B. A selecting unit 107 selects the output of the low-speed scrambler 105 during the timing corresponding to the bit rate A in a frame and selects the output of the high speed scrambler 106, during the timing that corresponds to the bit rate B in the frame.