To obtain the frequency modulator for FM synchronization broadcast where phases of modulation waves are kept identical.

A voice delay circuit 3 adjusts and corrects a phase difference of voice signals (a) by a voice delay circuit 3 and the signals are sampled by a sampling circuit 4. The resulting signal is converted into a digital voice signal by a quantization circuit 5 and give to a protocol conversion circuit 6. The protocol conversion circuit 6 compares digital voice data (b) with data stored in a ROM 7 and provides an output of corrected voice signal data. A capacitor changeover circuit 8 changes a load capacitance of a crystal oscillation element with the voice signal data. A crystal oscillation circuit 9 generates a carrier. An FM modulation section 10 changes the load capacitance of the crystal oscillation element to modulate the frequency and produces an FM broadcast program.