To automatically adjust a phase without the need for any adjustment at each relay station by selecting a prescribed period of a super-frame of an orthogonal frequency division multiplex signal to have a time longer than a maximum delay time among delay times of a broadcast wave among a transmission station and a plurality of relay stations.

A synchronizing signal inversion transmission 19 detects inversion of a super frame synchronizing signal that is inverted and transmitted for each prescribed period longer than a maximum delay in an SNF area to reset a write address of an FIFO 21. An OFDM signal written in the FIFO 21 in the unit of super frames is read in timing of a reset signal RR of a read address with the same period as that of each super frame on the basis of an absolute time T of the GPS after the input of a reset signal WR. Thus, a plurality of the relay stations placed at different places generate the reset signal RR of the read address at the same phase.