A device for transmitting digital broadcast signal comprises: at least a first encoding unit, each of which encodes data of a sub-channel with forward error correction encoding; at least a time-domain interleaving unit, each of which receives data output from a first encoding unit and performs interleaving in time-domain on the encoded data; a first multiplexing unit, which multiplexes the interleaved data output from each of the time-domain interleaving unit into Main Service Channel (MSC) data; a second encoding unit, which performs forward error correction encoding on a second set of data to obtain Fast Information Channel (FIC) data; a differential modulating unit, which performs differential modulation on the FIC data by using a first modulation mode and on the MSC data by using a second modulation mode, wherein the modulation level of the first modulation mode is lower than that of the second modulation mode; and a frame generating and transmitting unit, which generates signal unit transmission frames by using differential-modulation symbol sequences generated by the differential modulating unit and transmitting said signal unit transmission frames.