To reduce an average transmission signal power while keeping the transmission characteristic of a conventional complementary sequence repetitive modulation type comb-line spectrum communication system the same.

A transmitter side of an information signal uses N (N=2n power of 2, and n is an integer of 0 or more) sets of 0-attached extension sequence that is generated by attaching K-chips (K≤L) of 0s to the outside of a front part and the outside of a rear part of a repetitive sequence with a length NL consisting of N sets of self-complementary sequences each consisting of N sets of sequences each having a length of L chips and an amplitude of ±1 for a spread code to apply spread spectrum processing to the information signal. A receiver side of the information signal uses N sets of chip- attached extension sequence that is generated by attaching K-chips of the rear part and the front part of the self-complementary sequence to the outside of the front part and the outside of the rear part of the repetitive sequence with a length NL consisting of N sets of the self-complementary sequences for an inverse spread code to apply inverse spread processing to the received signal.